Minthara and Lae'zel.

The only 3 at this point in the game that, if they used the alignment system, I'm sure would be one type of evil or another. I've had a couple surprise moments where all 3 join in a short discussion, playing off each other's lines. I've had Lae'zel before, but I've never really kept Astarion around (unless I needed something with a DC of 30 lockpicked) and this is my first evil run, so Minthara isn't a smouldering pile of ash this time.