Fury: a powerful meta turned into a monster despite the efforts of the weaker (or in this case suboperant) mentor; may view younger metas as enemies; "hunger" for operants (lifeforce?)
Victor: ditto, plus an apparently murderous rage towards other metas replacing an initial wish to turn them to his will rather than see them form into a society
Kieran: self-discovered; attempts a global rise to power through control of operant lackeys
The decerebration of Isaac in the future timeline in S1x02 reminds me of the prehistoric Poltroyans' practice of brain cannibalization, but it would also seem to indicate that Sylar, or whoever the killer is, has some ability to make use of metas' brains.
What do you all think?