sometimes you just have to realize there are contradictions in the star wars saga. they say that yoda is the most powerful in one book, but then have windu defeat Sideous first....
and I have no quarms with the NJO luke being more powerful then the movie luke. I just am not willing to say he is more powerful then Sadow, Kun, or Revan. I would say probably after realizing that we were talking about the NEW JEDI ORDER Luke (make urself more clear)
that he would be able to bet malak and the exile
and since the ending of the story of Revan is Not Canon since there are two possible endings, I would Say that the entire dialogue dealing with weather the light side or dark side is more powerful in that part of the game is not stable information.
I would not be so quick to say anyone is the most powerful, although I am pretty sure that luke would take Malak while the Exile fought anakin and Revan killed Yoda. then Revan would take out anakin while Luke would kill malak and then they would have a Epic battle in which both of them would perish.