Someone so irritating that they are constantly on your mind in the way that a crush would be. They might even turn up in the odd fantasy.
Sarah Jessica Parker bugs me so much it's almost hot -- she might be my hate crush.
Having such a hate for someone that you start creeping on their Facebook to see what they're doing as if you have a crush on them. Most common in Ex's. For example, Checking your boyfriend's ex's page repeatedly to see if her pictures are prettier than yours or if she's seeing anyone or if she's talking to him.
"Did you see that she's in an "open relationship"? What a skank. I have the biggest hate crush on her.