Vader took part in blowing up a planet.... because they wanted a 'demonstration'.
Revan an exception? No, just no. Plenty of sith who were like Revan. Bane, Vader, Exar Kun. Kun wouldn't of wiped out a population center like that to take out 1 jedi. That's simply overkill and frankly stupid.
Malak while strong, and he did have a few moments of brilliance, he was more of a child snapping the heads off of puppies.
Exar Kun? oh please he wiped out the last of the Massassi race to become a spirit, he led the assault on Ossus, there were no lengths that Kun would not have gone to, to become ruler of the galaxy.
Bane is different yes.... oh wait, the Thought Bomb.