What makes a good LF2 Character?

[Kezeal]

In my opinion, a good LF2 character needs:
Fitting sprites(an NTSD character in the original LF2 wouldn't fit at all)
Original moves(just mix'n'matching LF2 character moves is not that interesting for me)
Balanced(or at least a bit. If you create a character with fitting sprites and original moves, but each move is an instakill, I won't want to play it)

These all were mentioned here, but most of you had more things you required. Just wanted to mention I'm glad with only these three.