Hate your co-worker or employee? Congratulations! Acknowledging you have a problem, after all, is the first step towards making things work out.
Ironically, teams in which everyone likes each other are typically weak teams. People (that includes you) have a tendency to like others who are similar to them. We revel in similarities. Grew up in the same town as me? You're awesome! Went to the same college? Hot diggity dog! Enjoy the same TV show as me? You're practically my twin. Gosh, you are amazing! With all those similarities, a team of copy-cats will have tunnel vision and won't have complementary skills. Great teams don't like each other nearly as much as they respect each other. There is greatness in differences.
Be Like Abe
Abraham Lincoln was famous for building a political cabinet of personal enemies. In a country that was polarized by a horrific civil war, Lincoln's genius was to assemble a cabinet of people who were his sworn enemies. Members of his cabinet may not have liked him (or vice versa) but it served what the country needed. He built a government where every American, regardless if he was from the Union or the Confederacy, had at least one person in the government with whom he agreed.
Your company has a mix of clients with different needs and demands of their own. Your company has a mix of things to do, which requires special talents. Your company needs diversity, but along with that may come personal conflict (just ask Abe). Here are some coping strategies.
Stop trying to like everyone. A big fallacy of managers is to believe they need to like the person they are managing. That is not the case at all. The manager just needs to respect what the employee does. And when I say "respect," I mean to see genuine value in a talent or ability of that employee. Stop trying to find things to like about the employee that you hate, just find something to respect.
Find the bigger enemy. My consulting group was engaged to help grow a business run by two sisters. The problem was finger pointing. Each sister blamed their struggles on the other, and they hated each other. That was until they found out their father was diagnosed with cancer. Immediately they had an enemy (the cancer) much greater than their hatred for each other. Instantly, they start to work together amazingly well. Seek to find a common enemy (perhaps a competitor) that you and the employee you hate can target together. A common enemy makes the best of friends.
Distance makes the heart grow fonder. Short, temporary bursts of disgust trumps a continual stream. If you just can't get over the fact that you can't stand the employee you manage, put distance between you and him. Put him in a different part of the office, or a different office altogether.