Although I don't usually play with them on, one problem with Sonic's moveset I have is his final smash, I feel like they could've used Super Sonic better, maybe instead make it a transformation final smash where he goes Super, then can fly around the stage freely, if he flys down into the stage he can land and use his ground attacks, and then when he uses his up special instead of using a spring he activates flight mode, his attacks are stronger and he doesn't take damage when hit, but he still gets launched away, so if he uses it at a high enough percent the opponent could launch him into the blast zone, after 100 seconds the Super form automatically goes away, so a good strategy against this is to try and keep launching him away from you so it wastes part of the time limit.
Of course, there are bigger problems that I have with the moveset because it actually matters in more competitive play, but I've always also disliked the final smash.