Just now I was playing KOTFE, Lady of Sorrows chapter. And in the end of the chapter my Dark Lord was riding in an elevator with Koth, Senya and Scorpio.

Three new companions, three traitors. I looked at them and started laughing.

Really, nearly every ally you're forced to take later betrays you! Koth. Scions. Lady of Sorrows. Senya. Aric Jorgan/Kaliyo (when they disobey you). The Emperor. And then, when it's FINALLY over, there's Theron!

Yay for Onslaught, where you are free to take revenge and betray literally everyone!

Koth only leaves if you go Dark, letting the factory blow up and let Kaliyo blow up the Spire. In his mind you betrayed him.

Senya pleads with you first. If you spare Arcann she remains loyal. If you don't she is honorable enough to fight you then and there instead of springing a surprise.

Scorpio deserves to be terminated. My Jedis spared her because they won't go Dark. My Empire characters will/did kill her, but maybe Agent will forgive. It could depend on if there's special dialogue for being a class story Companion to convince him. Haven't decided yet with Smuggler and Trooper. They are capable of doing it.

Theron is not a traitor. Extremely dumb, yes, but not a traitor.