Hm, I guess the key is how they are going to be enemies, and how that will be played out.
Like, is it a contemporary novel and they're enemies because they work at different places? Or they differ politically?
Or is it a fantasy novel and they're from different kingdoms? Maybe they get in a fight and both leave harmed (physically), but they're both warriors so they're not traumatized by that?
Or maybe they are enemies due to a misunderstanding (not sure if you're a fan of this particular plot device) and slowly they find out the truth.