Here's my opinion on this:
Kratos - His moveset is fine and should be left alone. The only things that need to be changed are this: Increase the recharge time/lower the range for his forward Square and decrease his AP rate.
Sly - Like Kratos, his moveset is fine but his supers are very unbalanced. His Level 1 is way too overpowered. I would suggest decreasing the distance that Murray can charge. Also, increase how long his Level 2 lasts. Why? 2 reasons: For one, it's so short and avoidable that it's almost a waste. I say increase the time for his Level 2 so that Sly users will have more incentive to use it and not abuse Level 1 so much.
Drake - This character is perhaps the most spammed character in the game. Now, there are plenty of legitimately good Drake players that put me to shame and I am not annoyed at that. They are just skilled players. However, I have seen people spam his down Circle and forward Triangle (the barrier, then machine gun thing) and it is VERY irritating. Superbot needs to fix this. Also, decrease the amount of times people can spam his barrel move.
Radec - Okay, I am so guilty of this (I main as Radec) but his sniper rifle move is SO spammable. Even though I would really not want Superbot to do this, they should increase the delay between each shot. That move created freakish amounts of AP in the Beta so I'm glad they changed it in the retial but it still might need to be a nerfed a little bit.
In my opinion everyone else is pretty balanced, including Toro and Raiden.
Ok Im a pro with Nariko, a prefectly average character, and I have to say if anything the only character who needs to be nerfted is kratos.
but if i was to have a list of characters who need to be nerfed, the characters It would be
2.sak boy( spaming his cake canon)
3.Raiden (counters everything, hes counters even work as projectiles) yes iv seen it happen
4.Radic (....*sigh*you already know why hes in my list)
1/6/2013 - Defeated the #1 player in the World in a Ranked Match.
Currently maining: Parappa
Future mains: Zeus, Issac