I've played only one For Glory match so far (and it was against Sheik) so I can't comment. In For Fun, Little Mac often makes a strong showing but nothing OP; it's Bowser who tends to give me the most trouble, but a lot of that is because the way he fights is something I'm not used to -- I like to run under people and up-smash them as they fall, and against Bowser, that is
a very bad idea. However I discovered recently that Ike's up-smash has priority over Bowser's butt-stomp
. In a match that I completely owned as Ike, no less.
Anyway, it's been only a few days since the game's NA release, and in most "pro" tier lists I don't usually see Mac up top. Top ten, but not #1. And tier lists are fluid so I wouldn't be too worried.
Of course that's assuming high-level play, and tiers vary at different levels, so maybe Mac
is OP for mid or low play.
But not in For Fun, at least, and wouldn't it take considerable skill to take advantage of any OP character's ability?
I've really enjoyed the balance of all the characters, myself. Some are more challenging to fight only because they force me to rethink my strategy, as with Bowser, but that's not the same as overpowered. I think the fact that the tier lists differ significantly by region (Nintendo's actually keeping track) says a lot of good things for how well-balanced the game is.