I have a aggressive fox in this game, and I am trying to develop a more defensive secondary. I would like a character that can shut down approach options, and also force the opponent approach, though they can't.

If any character fits this criteria, or close to it, please suggest it

Main Secondary

is the ultimate defensive character, Meteor is all you need

This too. I have nightmares 1v1-ing his BM

If you want to put some work in samus fits the bill i feel.

I'd avoid Sheik or Marth if you're like me, because the temptation to go aggro is too much and it does work with those characters. Naruto, BM, Link, and Samus are all great. I'd also recommend perhaps the puffballs as options? They do have to approach against projectile users, but they usually play a bit more defensively.

Well guys, I tried out your suggestions and the final decision is

Main Secondary

I found his projectiles (especially bombs) to be the most useful and variable with forcing and stopping approaches out of Black Mage, himself and Samus. And whenever the opponent did get in on me, I was able to either get them away or do a good combo better than the others

With Black Mage, meteor was very hard to use too slow, was easily avoided, and once they got past, all I could really do was space a forward air or do a smash attack , which didn't give enough distance to use Meteor again.

Samus was in the middle of the two, but the missiles, morph bombs bombs and charge shot just did not measure up to the adaptability of Links bombs. And when they got in, the Master sword and bombs were the better to get the opponent out than most of Samus' attacks

I agree with that as I used to main Sheik, Marth and Naruto, and with all of them, I was playing like I play with fox. I tried both puffs once or twice and they are defensive, but not exactly what I was looking for.

In my honest opinion, A Good Zero-Suit Samus is a nice pick for ranged and defensive play, however you can also take it up with a very simplistic and strategic Black Mage.

The frame data and move sets for both characters and great, so highly recommend these two.