Unfortunately (or fortunately, depending upon what way you look at it) I've been in that position many times. I've been in the position a few times where I've not only had to work with someone I can't stand but I have actually been their boss! That makes me sound like an intolerant person but I promise, I'm anything but.
If you simply work with them, on a similar level, you have a number of choices. You can ignore them and hope they ignore you in mutual dislike and disrespect. That can work in certain circumstances but it's better to try and achieve a mutual understanding in the sense that you're both stuck with the situation and you have to make the most of it. Liking each other is not compulsory - working together may well be, at least in the short term.
If you are the boss, you don't have that luxury. Your first objective has to be to find some form of common ground on which you can reach out to and relate to that person, ideally non-work related. It may be the shared admiration of a sports' team, it may be a shared interest in a leisure activity - it may be (but less than ideally) a shared dislike of some ideology or entity. Whatever it is, the two way respect issue is essential.
Bottom line? Common ground is desirable, mutual respect at least is essential - however much it may go against the grain...