Not only this, but he fractured the Sith into those who beleived that he was the rightful Sith Lord, and those who weren't so sure. This meant he had to go about the time consuming business of turning Bastilla to the Dark Side. So he got rid of Revan when the Sith most needed him/her, to use his keen tactical mind to counter Bastilla's battle meditation. When he betrayed Revan, he actually left himself in a very bad position- it was the height of a war which, with Bastilla's help, was beginning to turn against the Sith. Like a 'bitch' as some people would have it. In looking for the Star Maps and defying the Jedi Council, he wasn't so much betraying the Jedi as just following Revan. The art of betrayal is to time it so as to get yourself in the best possible position for you.
Was easily a greater master of betrayals than Malak.
