NEW YORK (AP) -- Former NFL defensive end Greg Hardy says he is "haunted" by his high-profile domestic violence past and wants to prove he has changed as he makes his debut in UFC, a promotion that hasn't hesitated to embrace fighters with legal or drug problems.His co-headline spot in a heavyweight bout Saturday night comes at a key moment for the MMA giant, its first show in its $1.5 billion contract with ESPN.While still playing football, Hardy was convicted in July 2014 of assaulting and threatening a woman who contended the 6-foot-4, 275-pounder threw her in a bathtub and onto a sofa covered with guns before threatening to kill her.