My complaints about fighting games will be very mild. I'm just thankful to be alive, and have stronger complaints about other stuff.
Moves that have incredibly difficult inputs in this game & others that I'd at least like to be able get to complete a character's command training, etc.
Combo challenges that are insanely difficult. I actually managed to do all of Leon's after many months, but for most other games, finishing them all for a character is impossible for me. KOF13 is the craziest, where even the 3rd challenge is impossible to me for some characters.
Games that have a huge gap between top & bottom tier. Updates help with this, and player skill makes difference. Ideally game testers catch this, though, no matter what the roster size is.
P4AU's odd color card leveling system. Your color only goes "up" if you win 10 matches of the same color card as you. Beating people higher than you won't help. Lose 10 matches vs. the same color & the color goes down, even if you've won 100 matches vs. higher colors. Ha, maybe this'll be fixed in an update.