Dad's a Terminator.

Your dad, the Terminator, was in love with you, but you signed a contract to go off to war. Five years later, you returned and thought no one was waiting for you because your partner had cheated on you. You were standing there clutching a machine gun, feeling a dull pain in your chest, and then your dad runs up to you and starts sobbing into your shoulder.
-ALIVE! ALIVE!
Dad Terminator wasn't your father.

Dad is usually rude and strict, but when he's with you, all his pride breaks down. Yes, he might hit you, but only if he's drunk or angry; he won't just touch you.