DC boast plenty of brutal characters however I have shortlisted a few witch the brutal being at the bottom.
While not actually killing people, old Brucie boy has snapped more bones than you can count. With his interrogations scary to say the least, you do not want to get on the Bats bad side.
Slade Wilson. Poor guy. His wife hates him. She shot his right eye. Part of a failed super soldier programme. Oh wait I forgot to mention he makes millions off of high profile assassinations. He is quite the contrary of a poor man. Slade is the king of assassins and wastes no time in killing his targets with either a gun or his sword. So brutal. And when you consider he is only #4 imagine what else is here.
3) Jason Todd
Jason Todd. Tortured by Joker. Killed by Joker. However reborn, he is the ruthless vilante Red Hood. Using guns and snapping necks earn him my respect and 3rd spot in this list.
Bane may be drugged up. But that doesn't change the fact he broke Batman's back. The friggin Batman! With strength unrivalled to anyone else, some might call him more brutal than #1.
The king of chaos. Joker is #1 because his plans kill so many people and he simply doesn't give a damn. He loves causing people to suffer. He revels at being captured because he can concot his next master plan.
If you feel I missed anyone or disagree with the order please let me know in the comments.