It's one of my typical hairsplitting bits of metaphysics, but where behavior is concerned, I prefer to think of depravity (in the sense of energies directed towards ignoble ends) rather than evil (which I regard as at best a phantasm).
In any event, Trask wins hands down, and Gregory trumps all the other Trasks in spades. After all, Blair was fairly honest--he was a minister of Satan, and in his debonair way, he was fairly up-front about that. (One of my all-time favorite scenes is the climactic confrontation between Blair and Julia in the Collinwood drawing room in which he reveals the true nature of his plans for Adam and Eve. The good doctor exclaims "That's monstrous!" and Blair, with a quiet leer, purrs "It's SUPPOSED to be.")
Trask, on the other hand, CLAIMED to be working on behalf of the Almighty. We all know what his REAL agenda was. And there are so many like him abroad in our nation today...
G.