Build him support, his job is to harass and gank early game like a boss, by mid game, he can have black cleaver and frozen mallet to mess up some champs. Played right, he can win team fights. Swap the right hero at the right moment, flash out if you can, harass and cc everyone you can with charge and your frozen mallet.
Make the best of your early game cause that's the only time where you will be able to dominate. Late game just focus on the enemy carries cause thats the only way you are really gonna contribute.