There's a difference between strong and cheap AI.
Gambit most definitely crosses the line, being able to break out of your combos and start one of his own. Without that, his AI would be much more bearable. His supers seem fairly fine, though. His card tossing can be avoided fairly easily, and his wildcard attack is just that: a wildcard. Sometimes it hurts, sometimes its meh. The attacks themselves aren't a problem, it's the AI behind them, in my mind.
Ironman, atleast in my opinion, is probably the most balanced of them. He's actually fairly interesting in my opinion. Very few combo-breaking shenanigans, and some interesting moves. Hulkbuster hits hard, but is fairly easy to get rid of. The House Protocol hits a large area, but does fairly low damage to compensate.
Carnage's AI can do the combo-breaking stuff I mentioned with Gambit. There's also his web-slinging, which he has the odd tendency to do several times in a row. More odd than frustrating. There's his creepy carnage attack (for lack of a better name ATM) that can be blocked, though it still deals plenty of damage blocked. The attack can be avoided by dodging or teleporting, but I didn't exploit that. There's his Ultra Carnage mode, which makes him larger, but he's still able to be smacked about.
Ultron was probably the most annoying to fight. His combos are just as strong as with the other characters, and he can do the combo-breaking present in the others. More annoying are his summoned minions - one move, he summons three minions, all as strong as the Hulkbuster from above, but more annoying due to how there's three of them, plus Ultron himself. As a result, they're much more difficult to get rid of, and most likely will deal a ton of damage. His other minion related super involves him summoning a whole legion of robots, who hit you a bit and then leave. Kinda like House Protocol, but much more annoying.
Remilia Scarlet: http://www.mediafire.com/download/d7kc30a1vyz6e3q/123THchars_M.7z Sakuya Izayoi: http://ricepigeon.webs.com/charactersmugen10.htm Joseph Joestar: http://www.mediafire.com/download/xl3wq7h33c8d747/joseph2.zip Youmu Konpaku: http://kurogane452.g.ribbon.to/ Youmu's Voicepack: https://www.mediafire.com/?0le6jgyvr5xg8
Rainy Ruins: http://excahm.tier-1.us/2013/12/aquapazza.html SDM Clock Tower and Hakurei Shrine: http://nightpalace.jimdo.com/m-u-g-e-n-stages/ DMC4 Forest: http://www.mediafire.com/download/u66z6g4hy626t7f/DMC-Stages.rar
BGM1: Astral Power, from Angel Sanctuary BGM2: Hong Meiling's theme, from Touhou Hisoutensoku BGM3: Dante battle theme, from SMT3 BGM4: Dichromatic Lotus Butterfly ~ Ancients, from Touhou 7.5
Appears on these pages
A rather recent version of Carnage with completely custom (if not a bit unorthodox) gameplay...