Xalek. Makes absolutely no sense for a LS Inquis - even the dialogue options when you get him are pretty much "Evil", "less evil", and "evilish-neutral".
No sense at all? Thats an awfully self-righteous attitude for someone who has slaughtered dozens of sith acolytes and has been complicit in the death of uncounted innocents by the time Xalek shows up.
LS Sith are still Sith, not misplaced Jedi. They've passed the trials at Korriban, after all.
My evilish-neutral Assassin wanted her fellow Twi'Lek as an apprentice, but she had to admit that Xalek's determination and force potential were quite impressive. He deserved a chance at life as much as she did. And since the alternative for him was death....