My favorite DC villian is Darkseid. All he has to do is shoot you with his omega beams and erase you out of existence. One of the most popular villians the King Jack Kirby has ever created.
One of the greatest villians who kicked the living shit out of Superman (pre crisis). Mongul. In Superman annual #11, written by ALan Moore. Mongul crashes superman's birthday party and traps superman's mind with a parasitic creature that made him think that kryton never blew up. Mongul then whoops Wonder woman's ass all across the fortress of solitude, while Batman and Robin watches because they really can't beat him.
I gotta go with Deathstrike (identity crisis and on) Hes a master of weapons, he has amazing palnning ability, he's in top pshyical condition. THe isssue of Identity Crisis where he nearly takes out half of the JLA by himself is just awesome.
Aquaman, because no one gives a man who can talk to fish any love. You tell me what other super hero can make a fish his bitch, and that horrible image will disappear.