Same that's a big thing for me aswell. Boxers who bounce back from defeat or can get off the floor to win. Of course the fact they can KO their opponents always helps aswell.
heart, determination, and focus and a little power with the want to stop his opponent and erase all doubts of who wins
Style. Some fighters just have a style that appeals to me(usually aggresive fighters) regardless of ability. I'm a huge fan of Joe loius, Marvin Hagler, Miguel cotto & Manny Pac
for me its ability. I like fighters who can do amazing **** in the ring. Things that other fighters just can't.