Mictlantecuhtli

Force Crush: Gained by any dark side player, not exclusive to the Sith Lord.

As to the corruption ability a Sith Lord has, you can turn the majority of your characters 90-100% evil(even the good ones) through manipulation of your personal alignment and party influence gains even without the class. Each time a character gains influence they shift towards your alignment, just have to balance influence/light side gains with the available dark side gains to end with an evil party and your own character with full dark side mastery.

Because light side gains reduce you from pure dark side to something less evil, it's very very difficult to get a good character to turn 100% dark side but you can get them very very far into the red as long as you rebuild the main characters dark side mastery after each heavy light side shift.

The only character you cannot make evil is Kreia, but considering she becomes evil at the end regardless it's within the realm of possibility to have a visibly evil party by the end of the game. This requires you use unlimited dark side point glitches at least once(Citadel Station, and use the glitch prior to gaining alot of influence with Atton through the murder of the guy who catches you stealing, etc for maximum dark side shift with him).

My last game before I stopped playing for a bit I had managed to turn these characters 90-100% to the dark side before the end of the game, just by manipulating their alignments with my own during influence gains. Obviously the evil characters were easier to do since their influence gains are dark side already(and Bao-Dur's dark side influence gain on Nar Shaddaa which should be used to get your character back to dark side mastery and gain influence with him simultaneously instead of used while you are already showing a dark side mastery bonus), and helpful for rebuilding dark side mastery after a light side gain from other influence oppurtunities.

G0-T0
Hanharr
HK-47
Mandalore
Visas
Atton - Becomes as pale, and creepy as the main pc.
Bao-Dur - Looks similar to Darth Maul.

That just leaves T3, and Handmaiden to be corrupted(with the focus being on corrupting Handmaiden over T3 since G0-T0 is more useful), though it was my first time making an "evil party" so I didn't really try corrupting these two but simply ignored them, and left them on the ship. T3 may ultimately be the only character you couldn't turn evil effectively in the game without harming the PC's endgame dark side mastery(and your oppurtunity to see them amongst the sith lords on the title screen).

I can easily do without the title of Sith Lord in the game, as I don't need it to corrupt my party members.

This of course also works in reverse to make evil characters good throughout gameplay, but I have never tried and probably never will.