Hunter Zolomon. I mean, this guy has had his mom killed by his father, accidentally caused the death of his girlfriend's father, thus putting an end to their relationship, and got his back broken by Gorilla Grodd, crippling him. But Zolomon didn't just put up with this; he turned into the awesome Zoom, Wally West's teacher, ultimately making Wally's own wife have a twin miscarriage in order to show Wally what real suffering is.
Aaaah Joker. What's not to like? He cracks jokes no matter what the situation is! Pit up against the entire Justice League armed with nothing but a box of toothpicks? Just whip out some puns! Plus he is the reasons Jason Todd/Red Hood is what he is today, so I have to give props for him, since I love Red Hood.
When he's not jobbing, this guy is an awesome Superman villain, and a general cool antagonist. His Omega Beams powers are really neat and interesting, and even commands his own planet Apokolips. He pimp slapped Superman for crying out loud! That automatically grants me his respect.
Sinestro, Sinestro! Great as a Green Lantern, and even better as the leader of his own Sinestro Corps, ruling the galaxy with an iron fist of fear. This guy is one force not to be reckoned with, and is a great Green Lantern (mostly Hal Jordan) villain. It's funny that in Secret Origins he called Hal a rookie and yet now he's considered his successor.
5. Lex Luthor
Seriously, how does this guy keep tricking the DC Universe? How many times has he run for President or some other government position claiming he has reformed and changed his ways? He's like the Norman Osborne of DC, but more evil and waaay more powerful. He's also wicked with prep, and could even rival Batman himself.