No need for anything like that imho. It might just make the other players feel useless in fights against them and you shouldn't do that.

Just ask him not to optimize too much, perhaps take t4 or t3 class. Fill the dungeons with plenty of traps, curses etc besides monsters. Add some puzzles, riddles ... It'll keep him and the others working, as they will all be challenged.

While he might've some edge with monsters, traps and curses, he might not be working on his CONSTANT VIGILANCE and might walk into a trap, has a curse bestowed upon his person, ...