I obviously write a huge range of characters but... The ones I get really obsessed with are the ones who dedicate themselves to a cause out of lack of direction...
Foreas in my comic decides to help the hero purely because he is the only person he cares about at the time and he hates his normal life... and he is also one of my favourites. Then there's Neptune who travelled the world and learned to fight purely to distract herself while she ran away from her mistakes. (no spoilers here)
I've also got a character in the works who becomes a contract killer purely because he is uncomfortable living a normal life after events of his past. He even adopts a kid purely because he thinks "Well, someone's gotta be his dad."
Hell, I've got a character who formed a mercenary group just to do some soul-searching after her dad died.
I have a type... yeah.