meaner than a junkyard dog
Exceptionally cruel, spiteful, malicious, or violent. Her dad is usually a pretty nice, chilled out guy, but he's gets meaner than a junkyard dog when he's been drinking. Don't go messing with that guy! He's meaner than a junkyard dog—he'll rip your head off just for looking at him funny!
meaner than a junkyard dog (with fourteen sucking pups)
Rur. cruel; eager to fight. Don't mess with her. She's meaner than a junkyard dog with fourteen sucking pups. They say Jim's meaner than a junkyard dog, but really, he's a sweetheart.