Ronny Boxer

Ronny Boxer was a vicious criminal from Batman Beyond who once kidnapped Bruce's dog, Ace, for use in highly illegal dog fights until a police raid managed to free Ace and temporary put Ronny out of business.

However Ronny would return later as the new Batman tracked the criminal down and finds out that he is back to his old tricks, only now he is using mutagenic drugs to turn dogs into literal killing machines.