Mmm..another idea hit me while I was in the car. This one is before modern times in a fantasy setting, where there are slaves and other such things.
My character would be a slave, conscripted into Gladitorial-esque games. A rippling physique toned from days-on-end of combat and fights. He bares a few scars from his battles, but he has also been nearly undefeated the entire run. This is why he is chosen to go on a quest, and why your character is sent along with him. You see, your character will be his Moderator, a limiter, if you will. My character is supernaturally strong, but has seals upon him that can only be temporarily lifted by your character, who can of course fight on her own as well. He's chosen to go on a quest that, by all rights, is a suicide mission that everyone on the council is hoping he will die in to finally be rid of him, as the Gladiator games aren't doing the job. However, they also see the need to get the job done, which is where your character comes in. She's been instructed to abandon him as soon as they reach their destination and he engages the enemy forces, leaving him to die while also letting him use his full power to make sure the job gets done in secret while the enemy is distracted.
However, the two have a long trip ahead of them, and perhaps as the move along in their journey, your character could find it harder and harder to keep her mission in her mind, where he has to be killed/left to die...perhaps she starts to learn more about him, and that changes her view not only on him, but slaves/gladiators as well? :3