evil to the core

Completely and utterly bad, evil, or corrupt. The defense attorney refused to take the case when he realized the criminal was evil to the core, unrepentantly boasting about his heinous crimes. That company is just evil to the core—I wouldn't be surprised if all the employees were embezzling money! I always knew that guy was evil to the core. He'd turn against his own mother if it would help his ascent to the top!