There's a reason why Kenneth David Kane has the nickname 'Killer'. He's a violent, murdering psychopath who murdered his wife Annie, Max's mother, with his bare hands. Although Kane might like to think that he's been rehabilitated inside prison, and that he's now a changed man due to his embracing Christianity, in actual fact he's the same dangerous criminal he was when he was first locked up.
Kane proves that he's still a bad guy after he busts out of prison. The first example that he hasn't changed at all comes when he kidnaps Max from his grandparents' house, and on Christmas Eve too. This simply isn't something that a rehabilitated, God-fearing Christian would do. As one can imagine, Max is terrified by the experience, and the fact that Kane is willing to subject his own flesh and blood to such fear is a further sign that he hasn't changed at all; he's still a bad guy.
As we've seen, Kane claims to have found God while on the inside. But this is proved to be another lie when he swears on a Bible in front of Max that he never killed his mother. Kane did in fact kill Annie, as he knows full well. Yet in true bad guy fashion, he blatantly tells a whopping great lie on the Good Book itself. The man is utterly shameless.
'Killer' Kane proceeds to cement his bad guy credentials when he tries to kill Loretta Lee in the exact same way—with his bare hands—that he killed Annie. Loretta valiantly tries to free Max from his dad's evil clutches, but is caught in the act by Kane, who proceeds to strangle Loretta to within an inch of her life.
Max manages to distract his dad just long enough to get him to let go of Loretta's neck. He does this by telling Kane that he knows that he killed his mom. Kane responds like the bad guy he is by squeezing his powerful hands tight around Max's neck. Thankfully, before Kane can do any more damage, the police arrive and order him to put his hands up.