Event 1 - Troubled King
A rank is around 10-20 seconds.
S rank is around 10 or lower
For Mario's First Stock, F-Air him into oblivion.
For his second, you may do it again, or you can just wait in the right side of the map and Back-Throw him.

Event 2 - Fleas
A rank is around 22-25(?) seconds
S rank is around 21 or lower.
I actually recommend spamming Dash Attack instead of Down-B, because Down-B will cause them to Star K.O, wasting your time, while it can still get you to A rank Dash attack is easier tbh.

Event 3 - Gourmet Race
A rank is around 269%(?)-271%
S rank is lower(?)
There is no actual method for this, not only that the other enemies can't damage you for less annoyance, but they can steal your food.
The only method here is to trust the RNG, because each food gives different % and spawns randomly.

Event 4 - Battle Revolution
A rank is around 33-36 seconds
S rank is around 32 or lower
It's another RNG based match, there's no actually any method here aside from stroking grabbing and sucking throwing Pokeballs.

Event 5 - Rockin' Blues
A rank is around 17-20 seconds
S rank is around 17 or lower
The best method here is to throw them/F-Tilt/F-Smash to the blastzone.

Event 6 - Saving the Saturns
A rank is around 6-%10%
S rank is around 5% or lower
It's one of the most irritating Events, like really.
BUT, after doing this a couple of times, I actually realized Luffy is throwing the Saturns to you, so whatever you do you must stay in the pool, not only because it regenerates you but also because you can defend the Saturns there, and even if he did got one of the Saturns, he will throw it at you and not to the blastzone.

Event 7 - Who Needs Turnips?
A rank is around 27-30 seconds
S rank is around 27 or lower
It's one of the easiest, but also one of the most RNG-based amongst them.
Just keep using Down-B and throw all of those at Bowser, he won't know what hit him.
Sonario: Reset till you get Home-Run Bat.

Event 8 - Opposite Day
A rank is around 20 seconds
S rank is maybe lower
It's one of the most irritating ones, but just stick close to Bowser and you'll most likely Not be fine.

Event 9 - You're Too Slow
A rank is around 3-5 seconds
S rank is 2 or lower
My best method here is to keep retrying until you get into the 3P spot of the map and spam ZA WARUDO Stop

Event 10 - Tag You're It
A rank is around 38-40 seconds
S rank is lower.
I can't probbably help you with this. Since Exploding Tag is really slow you must do hard reads and you must rack them damages up.

A rank is around 35-40 seconds
S rank is lower
Just use Sandbag and Side-B them into oblivion. Though I might recommend to reset a couple of times for Mario since those platforms are interrupting your Side-Bing to oblivioning, reset until you get the layout with only 1 platform in the middle.

Event 11 - Lagggggg
A rank is around 16-20 seconds
S rank is lower
Pfft, just back throw/forward throw them out of the stage then D-Air. They will SD a couple of times too so use that to your advantage.

Event 12 - Shadow Clone Showdown
A rank is around 17-20 seconds
S rank is lower
The one who uses Up-B is the real one (aside from you you stoopid) there are some times that the real one will SD but you can't wait for that s***, so immediately find the real one, throw them out of the stage and F-Air them.
Although if your really lucky the real one might be the nearest one to you.

Event 13 - Combo Maker
A rank is around 50-60 percent I suppose?
S rank is maybe around 61 or higher?
Use Marth, Dash to Sandbag>Jump>Spam F-Air and Dair (to make this easier use C-Sticks)
But, since this Event doesn't base your rank from the time you made a 50% combo, and since your Smashified and Weaponised Autism wants 999 score.
Use Fox, Shoot laser till 999>any attack.

Event 14 - In the Ballpark
A rank is around 26-30 seconds
S rank is around 25 seconds or lower
Start with Jiggly first because the f***'s a lazy a** and wants to stay in the wooden piece of s*** made by a bunch of s*** pixels,
then Kirby because the f*** wants to live a quiet life and has a Succ fetish, then Pac-Man because he's annoying as a a f*** fly.

Event 15 - Sworn to the Sword
A rank is around 1 minute
S rank is lower
Just F-Air/F-Throw everyone into the Purple Realm so that you could make that f***** Kirito and s*** CGI Guts be jealous of a much better swordsman.
Or you know you could just do some combos like a s*** Lloyd I am you are.

Event 16 - Bounty Hunting
A rank is around 17-30 seconds
S rank is 16 or lower
Basically just throw Green Yoshi outside of the stage then D-Air him.

Event 17 - Dark Link's Advance
A rank is around 25-30 seconds
S rank is lower
There's no method here, just play Link like a cool guy and just kill the s*** out of that Edgy version of yourself

Event 18 - Target Race
A rank is around 1 minute and 20 seconds
S rank is lower
Using Fox might be the best choice here, dang Fox and his Blaster shenanigans

Event 19 - Nightmare in Dreamland
A rank is around 50s-1minute
S rank is lower
This is quite a problematic one, though I think starting with Meta Knight is a much better idea, the dude's a lightweight meaning he can be killed quite early, don't worry about Kirby the guy just wants a quiet life in Dreamland, he won't let anyone ruin that life.

Event 20 - Speed Demon
A rank is around 13-15 seconds
S rank is lower
There are two methods here:
Be 20GX and Falcon Punch that Sonic after he says "WATASHI WA SHINEN! SHINENZUUUUU!"
Or be a boring one and throw him to the left part of the map and stomp him,

A rank is around 1m 10s
S rank is lower
Use Sandbag and do the usual, as usual.
But Naruto and Sora's map is annoying so you probbably need to take them out in another way and faster too.
For Sonic just wait till he gets to you and Back Throw him.

Event 21 - Battle of the 99 Heartless?
S rank is lower than 1:30
Just stay in this spot

and spam U-Tilt, face at the left side too so you don't need to worry about the G&Ws spawning at the left side of the map

Event 22 - Role Reversal
A rank is around 10-11 seconds
S rank is lower
To get a better score, retry till you get Jigglypuff, Jiggly will jump around for a moment which allows you to easily catch up to her

Event 23 - Meteo Campaign
A rank is around 1m and 20s
S rank is lower
Personally, I prefer the D-Air.
Though to be serious, stay in the bottom platform and just B-Throw>D-Air, it might not work sometimes tho.

Event 24 - Restless
Reset till you get into 3P position, then use Sing; title is clickbait, don't use Rest for gods sake.

Event 25 - Luigi Takes Charge!
Mario asks for a day off which causes PP to be kidnapped.
A rank - 5 KO
S rank - 6 KO
Since Luigi doesn't really have any Meteors here (He has one in his D-Air but that s***'s hard to hit), I guess B-Throw to B-Air>B-Air>B-Air is a good idea.
riku234: At 0-10%, do this combo: U-Throw > U-Air > U-Air > U-Special
Sonario:

I USmash and UAired him close to the ceiling before fire punching him here.

Bowser got star KO'd almost immediately.

Here are the (badly cropped) percentages. Bowser's jumped from 62 to 84 because of the Fire Punch. The USmash/UThrow-UAir-UAir-UpB combo can 0-death Bowser easily.

If you get him high enough, it even KO's bowser at around 40%.
Also if, Star KOs take too long, you could always BAir/FSmash him away.

Event 26 - Cleaning Duty
Not sure about the Ranks.
To get an S here you need to kill Wario, along the way you must clean a bunch of naughty stuff too.
He can SD sometimes but B-Throw out of the stage to D-Air might be a great idea.

Event 27 - Monkey, Dee, Luffy!
A rank is around 26-28 seconds
S rank is lower
I have no method for this, so please tell me if you know any.

Event 28 - Bomb Factory Malfunction
A rank is around 30 seconds
S rank is around 40 seconds
This, s***'s, irritating.
I don't really think there's any method here aside from trusting RNGesus, because f*** hell those Bombs are uggggh
Oh, you can actually destroy bombs too, maybe that's useful for someone.

Event 29 - The Power of Random
A rank is around 1m 20s
S rank is around 1m
Trust RNGesus, that's the only method here.

Event 30 - At Your Service
A rank is around 30s
S rank is around 20s
Trust RNGesus as usual. Although a reminder that Goku can get those assist trophies too, so get all of those trophies first before him.
Bedoop: Restart until Assist Trophy spawns close to you
Goku will immediately dash for it
Back throw
Down Air

A rank is around 1m 20s
S rank is around 1m 10s
Sandba- wait what?
That won't work?
Nah, we Samus now bois.
For everyone except Goku, just B-Throw them out of the stage and D-Air them.
For Goku, just keep B-Throwing them out of Namek

Event 31 - A Heavenly Power
A rank is around 35s-40s
S rank is lower
No methods for this one.

Event 32 - McLeodGaming TIME
A rank is around 4s
S rank is lower
Lol Captain Falcon
Lol Dash
Lol Knee
Sonario: Use Luigi, use his Side-B/Green Missile and reset till you get a Misfire.
Bedoop: Sandbag
Run up to Falcon
Up B

Event 33 - Hide 'n' Shiek
A rank is around 1m 30s
S rank is lower
f*** this event really.
I don't think these Female Zelda's gonna turn into f*** Ninja Male Zelda for 2 minutes.
Anyways use Samus then B-Throw to D-Air them if they ever turn to Ninja Male Zelda.

Event 34 - Mega Microgames
A rank is around 50%
S rank is lower
Remember to dodge all of them attacks, your score is based from the damage you get.
For the games, play it like normal.

Event 35 - Biohazard
Lol Samus
Lol B-Throw
Lol D-Air

Event 36 - Gotta Cherish Them All
A rank is around 25-30s
S rank is lower
No method for this one, but apperently these newbies think using a Master Ball (no just because it's recolored doesn't mean it's a Pokeball, sorry) to a Pikachu is a better idea than using it on a Rattata.

Event 37 - Fist of the World King
A rank is around 21-30s
S rank is lower
Lol Chaingrab F-Throw
Lol F-Air

Event 38 - Pretty in Pink
A rank is around 35-40
S rank is lower
No method for this one, but try using Samus and do the usual.
riku434:Pick Kirby and spam Up B at the ledge and hope it spikes them off-stage.

Event 39 - Dawn of the First Day
A rank is 5 KO
S rank is 6 KO
No method for this one, just play Link like a normal man.
riku434: make sure Black mage starts of anywhere BUT the middle. If he does spawn in the middle at the begging of the match reset the event until he does no spawn at the middle. Once black mage spawns somewhere that isn't the middle let bowser come to you and back throw him and then down tilt as he's airborne. Down tilt is a meteor when it hits an opponent that is in midair. Link's back throw to down tilt is basically poor man's Samus's back throw to dair. It isn't SUPER effective in this event as you may have to attempt this method many times before you get an A/S rank but it's currently the most effective method i could find for this event.
Sonario: The last hit of Link's aerial Up Spec is a great finisher. Also, you could try to KO Bowser first because he doesn't have a crazy recovery.

Event 40 - The Mother Brain
A rank around 31-40 sec
S rank is lower
Just use Super Missile
Just use Super Missile
I'm not sure about the exact time for the charging, but I think it's around 3-5 seconds after the blink started.
Just use Super Missile
Don't use anything else
Just stay in that spot where you spawned
And use Super Missile

Event 41 - Down with Mario
A rank is around 30-40 sec
S rank is lower
No method for this one, because B-Throw to the Purple Realm is kinda slow.

Event 42 - Pacmania
A rank is around 6-8 sec
S rank is lower
No method for this one either, just use Pacman's Final Smash like a normal man.

Event 43 - Swords vs Spears
A rank is around 30 sec
S rank is lower
These Waddle Dees are cute, just like Caeda.
Gee Marth, you monster, why would you want to kill those warm and cute Smol Nozom- Waddle Dees.
Anyways, just spam F-Smash or be 20BC, your choice.

Event 44 - Climate Changes
The AI of SSF2 is s*** so use that to your advantage.
Retry until you get the 1P or 4P position of the map, then stay inside the cover, don't worry they won't go down.
Just wait till the Hazard get them, don't worry about their second stock too because they will always spawn at the top of the map.

A rank is around 1m 30s
S rank is lower
Use the Lol Samus Lol B-Throw Lol D-Air shenanigans as usual.

Event 45 - Bob-Omb Battlefield
A rank is around 30-50%
S rank is lower
Wow, an event where Bombs will drop? This should be ea-
Wait why is there a bomb falling during the countdown?
Why is it falling to me?
FFFFFFFFFFFFF-
Seriously that one's s***, so if a Bomb happens to fall to you just reset already lol.
Anyways there's no actual method here aside from playing like normal, trusting RNGesus or use the Bombs to kill Peach.
A little bit of reminder that if you die your score will be instantly 100%, so don't die.
Kirb-Star: Restart he event until the bomb touches Peach on the countdown, take as many advantages as possible.

Event 46 - Eggman Empire
A rank is around 50 KOs
S rank is around 60 KOs
Spammable moves are Up-Spec and D-Smash, other than that I don't know any other method.
Sonario: you could stay on one the platform to the right and spam Neutral Spec until it breaks. Then stay in the middle and spam Dsmash.

Event 47 - The Trouble With Doubles
Either use Fox, Falco or Samus.
Just kill the damn thing.

Event 48 - Pirate Attack
A rank is around 50-60s
S rank is lower
Cargo Shenanigans might work, though maybe B-Throw to D-Air might still work

Event 49 - A Night At the Casino
A rank is around 20-30s
S rank is lower
Just focus on the bumpers, start with the on the left, to the top, to the right and eventually to the bottom, ignore your opponent too.

Event 50 - Metal Clash
Not sure about the ranking
f*** this Event, really.
Use Captain Falcon, B-Throw to D-Air everyone if you can.
Focus on Megaman, then Bowser, leaving DK for last, since his Recovery is s*** and he falls faster than any girl falling in love with a guy.
Sonario: Use Side-B of Tails.

A rank is around 2m 30s
S rank is lower
You can use either use Sandbag Side-B shenanigans or Lol Samus Lol B-Throw Lol D-Air etc.

Event 51 - ?????
A rank is around 56s-1m10s
S rank is 55 and lower
Use either:
Zelda, spam U-Tilt
Samus, spam U-Smash
Also use those fireworks, they're really useful.
Also they can hurt each other sometimes too.
Rollaboy: I chose Pit, let the Master Hands wreck each other's asses. If they use a projectile, like, the HANDgun (lol), use the reflector.
Stay in the middle of the map as much as possible.They will end up triggering most of the fireworks anyway.
Bedoop: Spam FAir and Fireworks for decades

I USmash and UAired him close to the ceiling before fire punching him here.

Bowser got star KO'd almost immediately.

Here are the (badly cropped) percentages. Bowser's jumped from 62 to 84 because of the Fire Punch. The USmash/UThrow-UAir-UAir-UpB combo can 0-death Bowser easily.

If you get him high enough, it even KO's bowser at around 40%.