[quote=@Imaginary]
[@Automaton] What happens if his foe has an ability that there isn't really an "opposite" for? Like, my char does illusions...
[/quote]

Ah YES I was thinking of this myself. Since his ability is focused more around countering other peoples abilities I think he would gain the ability of Reality awareness?. 

The way I see it I imagine he has a whole bunch of stem cells in his body and when they come into contact with another mutants abilities or DNA they change to adapt to that. So once hit with an illusion they would send a message to the brain that says "this isn't real!". But that doesn't mean illusions and things like that are useless. For example if you made a snake appear and bite him and his body created the damage of a snake bite, he would get the snake bite but he wouldn't be fooled by that particular snake again. But if your character did it again but with more focus into it to make it more real it could fool the brain more. You know?, also Mental attacks don't count as me being able to counteract so if you made him afraid and see his worst nightmare as long as it didn't HIT him it will remain an illusion and he will be under full effects.