Hater (n.):
A person that simply cannot be happy for another person’s success. Instead of giving acknowledgment in courtesy, a hater often pursues his/her point by exposing a flaw in the target subject. Hating, the result of being a hater, is not exactly jealousy. The hater doesn’t really want to be the person he or she hates, rather the hater wants to knock someone else down a notch.