Ok, so I did do this in training mode, but I think some of the stuff i'm say here might still work when you face other players (MAYBE).
Also when I say a % like 120%, I mean doing the back throw up b while they are at the %.
The only stage I will test all this on is final destination.
Back throw to up b star KO/connecting:
kills at 111% and at 127% he gets out easily, but i'm pretty sure if you try this against someone else online, they can DI away from your up b earlier after being back thrown so it wouldn't reach (maybe) or away from the blast zone so it wouldn't ko at 111%.

can't even connect the up b at 70% forget it.

can connect at 76% but at 77% falls out easily.

star KOs at 120% (probably can DI out of it though).

129% doesn't star ko, but at 130% it does ko (gravity?).

at 118%

133%

123%

82% to 140% (connects so easily, can probably be DI early, but can still get her up to 140%, didn't bother see if you can still do it to her past it, maybe later).

75% it still connects and almost KOs, but doesn't KO. At 76% they get away easily.

68% KOs, but looks very easy to DI, but it can potentially still KO till she reaches 77%.

122% can do it even a 140%, didn't bother see if it you can still do it higher than that, but I think you can.

can KO at 81% and 82% but they look very easy to DI there. Higher % than that and it seems to easily KO him.

82% DI can maybe help, but KOs there. You can keep doing this to kirby between 82 to 91%, 92 he gets out.

86% it connects but doesn't KO, 87% gets out easily.

81% can maybe DI out, but should KO at 82%.

wont KO.

wont KO

75% it connects but doesn't kill, 76% they can get away.

can't even connect at 75%.

93% (can probably DI it).

99% to 101%(can probably DI at 99%).

connects 91% but doesn't KO

can't connect at high percent to KO.

almost KOs at 100% (if you do the small run after the back throw to up b it KOs, tho again, timing).

he keeps getting out past 86%.

same thing as

97% but can probably DI it, can do it till 111%, but can get out at 112%.

98% but can maybe DI, can keep doing to 125%, but past he can get out.

119% to 122%, can get out past.

connects at 89% but doesn't KO, 90% they get away.

97% connects but doesn't KO, past he gets out.

not even at 60% (the same thing I tried against

, works on

though at 117%).

doesn't seem to work on him at all to be honest.

81% it connects, but doesn't KO obviously.

Can connect at 103% but doesn't kill, and he gets away at 104%

110%, the thing is, when you do this to goku at 110% (or maybe a little higher), you can still catch him if you back throw, run quickly after and quickly up b before he's out of range of for the last hit for up b (so for this, you need good timing), this is the only way I see you can hit

with this.

117%
Because of how I tried to get the KO on goku, i'm go back another time and see if the same way works on other characters that I said could get out of it.
But some characters that can get out of it, it does seem like running a little bit right after the back throw into the up b
MIGHT work, but again, i'll test that out later, but hopefully online.. maybe..