i dislike the term "genius". It would imply that intelligence is the only worthy aspect.
That said, if you'll pardon my use of it, I tend to write characters that are a genius at one specific aspect. one character may be individually weak, but a genius at tactics, or one that has a hard time cooperating, but is a genius at individual swordsmanship. Or perhaps a mage that can memorize any number of spells, but when it comes to interacting with others, his speech turns basically complete gibberish. things like that. it tend to make it so there are genuine risks. You have a character that is individually weak but a master tactician, he can get in a situation where he must rely solely on his own strength.
have him win by outsmarting the enemy, or by convincing a passerby to assist, or some other means.