Mordenkaiden....it depends.
Is he stopping me from doing something crucial to the survival of myself or loved ones? If so, yes.
Is he just there twiddling his thumbs? If so, no.
Has he gone evil in any way shape or form? If so, yes. People that powerful go down FAST when they turn to the darkness.
But then again, Mordenkaiden does not exist in Faerun, or even Abeir-Toril, so it's irellevant.
However, I can tell you a story of how Drizz't Do'urden royally screwed with my character in a way that you'll have to read my story hour to find out...once I get to writing that part.

End result: Really dead Drizz't.
As for Elminster...*looks up stats in the ELH*...if my character had reason to take him down, he could do it easily. And his ward of
"You can't kill me because I'm Elminster! The pet NPC of some guy who was involved in writing up the FR! NYAAA!" would NOT work....at all.
