Vanilla Krentinel (Graal + Omniblade) ... doesn't have the glitchy lock-on problems that plague the Worlard.
QFI. Kills Phantoms and goons with a single application of tech bitchslap.
Collector using the around-corner telekinetic punch only.
Melee GI. Goes down in a heartbeat, but can destroy more enemies at once. Timing the pulses is easy. You have to listen to that sound cue from the heavy melee in order to spam it in succession.
These are all the best, along with the paladin, valkyrie, kroguard, sabotuer, vorcha sentinel, human adept, phoguard, vol-guard, cabal, the titbot and three or four others.
My personal favorites are:
1) Krentinel. Add the batglove and your backhands will decapitate. Mwahahahaha.
2) Paladin, also with the batglove so your shield bashes will decapitate.
3) QFI. Way back in the day, I figured out the sabotage damage boost.
4) Justicar. Lots of DR, and just because.
5) Havoc & Saboteur. Always loved the animations. AoE hydraulic death hop.