I would say something like that for Kreia, it is her force of perssuasion, to inflict doubt within the ennmy heart.
For Revan it the samething combined with a sheer willpower, and being a leader, someone that teach soem trick, someone who inspire allegeance.... I don't know how to properly formulate this.. But a guy clearly explain how can Revan can force th other to do his beding...
And here another link :
http://www.debate.org/debates/RESOLVED-In-a-fight-to-the-death-Darth-Vader-would-defeat-Darth-Revan/1/