The the savior complex in Atton is more present than ever in a dark side route (at least as a fem character).
When you do dark side aligned things (force persuasion (sometimes), lying/stealing (specifically in this case (what caused this post) taking Ahrnell's kinrath gland and letting him die) you get dark side points, and some people in your party will also get them (thats a whole other post).
I'm currently super close to True Sith, and my face is. awful (in a really really sick and cool way), and so is Atton's. When you talk to him, he goes
Atton: I don't know what that witch [Kreia] did to you, but she's dragging you down into whatever hole she came out of. I'm only saying this because there's still a chance for you to stop this before whatever darkness she brought on you eats you alive."
Exile: "I am stronger than I have ever been."
Atton: "Thats what you think, but it's going to rot you - the signs are already in your face."
i dont know if this is supposed to be implied, but to me it heavily feels like (esp. with the "[...] there's still a chance for you to stop [...]") that he's definitely only saying this because he longs to be the savior and protector. we see this on Peragus, we see this on Telos, we see it on Malachor V, we see it basically everywhere (when he's in the party, ofc.)
This combined with what happens when you kill the Czerka Worker on Telos (I couldn't find my video of it and cant find the dialogue online, so it wont be verbatim but instead what i remember until i can find it (i looked for a long 30 minutes) (i might have to start a new play through for it)
Atton: "What just happened? One minute we were just talking, then the next..."
Atton: "Yeah. Don't surprise me like that. Next time you're out to kill somebody, let me know first."
Like. idk abt yall, but if this super hot girl came into my life and started murdering people who were "in her way" (he wanted a way off the station and to safety and kindly asked to be shown the way out) i'd be a little more mad (plus iirc asking if he's okay actually adds to his influence which is honestly so relatable)
Atton is just a man with a dream (a dream to protect the woman jedi and either kill Sion or die in her arms confessing his love for her (which is also real))