I think it’s very easy to get into binary mode when you’re thinking about stories (or writing them). You know–Luke is good, Vader is bad. Protagonist-antagonist, that’s how it usually goes, right?
But I think there’s something to be said for tossing a rival in the hero’s way, in addition to the main baddie. You kind of get it with Rowling’s Potter vs Malfoy rivalry (though I don’t think it’s pushed to the extent that it could be). Malfoy’s not the Big Bad (that’s Voldy’s job) but he serves to hamper Potter on a day-to-day basis. Or to use another example, Indiana Jones kept bumping up against his rival Belloq, even though the main baddies were (of course) Nazis.
In your story, maybe that’s just what your hero needs. Someone to compete against, someone to make life difficult, maybe even someone to hate–but most importantly– someone he also has to live with.
Humble protagonist killing off powerful evil antagonist is the stuff epics are made of. But living alongside that one annoying dude day after day? That’s something we can all relate to.
I embrace my rival, but only to strangle him.