These aren't my top 5 per say but they are all badass.
1.Broly from DBZ, cause you know, he's Broly.
2.Toguro from Yu Yu Hakusho is the most gangsta muthafacko aroud with those sunglasses.
3. Greed from FMA although not ruthlessly evil, was still badass as hell and was even beating Ed's ass for thje first part of the fight while severely weakened.
4. Arlong from One Piece
5. Captain Kuro from One Piece, there are few things more badass than adjusting your glasses with 3 foot blades comin from your fingers.
He's only overly buffed at 20% and over, and he get's sickly buff at 80%, beyond that and his skin turns grey and he looks more demon. At 1% he flicked off a normal human's head(I think that's what he did, I only saw the English version of that ep. but it was implied that's what happened), that's plain gangsta son!
i forgot the name but the main villian from fushigi yuugi{curious play}
frieza
urochimaru
itachi
aizen sousake
the earl{d gray man}
naraku
char aznable
vicious/vincent{cowboy bebop}
knives
cain{trinity blood}
aion{crono crusade}
shishio
lucimon/yygdrasil/reaper mon/taimon/{digimon}
recca's brother
hades/lucifer{saint seiya}
cross{satan 666}
shadow the hedgehog