Just going over the Top Tier assuming Apex stagelist, if your character has a sword or items, you're probably going to be even or better against ICs.
Specifically:
MK: between +/- 1 in MKs favor to +/-2 MKs favor assuming solo ICs. In greater detail, it's between even and -1 on most starter stages and -3ish on MKs counterpicks that you're forced to if played correctly
Diddy: Probably even, if not slightly moving towards ICs favor. I personally think it might be the most even MU in the game that's not a ditto
Snake: Snake used to be considered a +/-2 hard counter and ICs hardest MU back in the 2009/2010 metagame. As the metagame has evolved, it's generally considered by most to be between even or +/- 1 in snake's favor as new things are developed for ICs
Marth: On paper, Marth kind of poops on ICs. But in practice, it's a MU that's show itself to be pretty even.
Wario: Probably even if played absolutely correctly, but slightly in ICs favor if I had to pick one.
Zero Suit Samus: Probably a solid +/-1 in ZSS's favor. Some notable ICs think it's even though, some think it's ICs hardest MU
Toon Link: Probably a solid +/-1 in Toon Link's favor. I think if it's played correctly this MU might be the hardest for ICs, but I'm in the biased minority of having the most losses to TL in tournament compared to any other player in the world. Some think it's closer to the even side than the -2 side.
Peach: Probably a solid +/-1 in Peach's favor
Rob: Probably a solid +/-1 in Rob's favor
Ike: I personally think it's +/-1 in ICs favor, but there's been some decent sample evidence that it might be even for Ike
One outlier is Wolf, who probably is even to +/-1 in wolf's favor assuming the wolf knows what they are doing. If they don't, then it has the chance to be ugly for wolf. But that's not really an outlier since Wolf has a sword on his laser gun
The other is Link, who is probably +/-1 or 2ish in ICs favor due to lack of mobility. However Link doesn't really exist as a character, so it doesn't matter if it's an outlier to the swords and items rule
Everything else is pretty well shut down by ICs spectrum of options