Kickback wants to be your friend. Not that he covets social interaction, it's purely to dig up your most embarrassing and exploitable secrets, so that he can make his new 'friend' do his bidding.
The only thing Kickback enjoys more than the recruiting process is destroying his reluctant double agents after they've exhausted their usefulness. A small kick from Kickback's powerful feet can punch a hole in plate steel.
Kick back was changed to a gunner in Release 1.24 and given a new ability during that change.
Kickback was introduced at the start of the game and is the counterpart to Cliffjumper.