Originally Posted by Nyloth
I would never compare Astarion to a Prince. Their common feature is only the love of power (and not same way). Otherwise, they are very different. And I understand why the OP sees common ground between Astarion and Sebille.

1. Master
2. Scar
3. Desire for revenge
4. Strong distrust

But Sebille is not a manipulator. Astarion manipulates, after the first attack, he immediately becomes a cutie. He says "trust me", and can kill you in the same night. He's also a chaotic evil, and I really hope that doesn't change. I can expect that even if MC supports him, Astarion will still betray us. But it looks more pleasant than "the way of redemption".

In DoS2 end Sebille became softer, and I rly don’t like it. I liked who she was, but not who she became. I hope that Astarion will follow path of evil, even if it ends badly, so be it.

I also didn't read spoilers, I don't want to spoil my fun.

I love the idea of an irredeemable character arc, but I did really enjoy Sebille and her story line, I just loved the development of character and the different ways acts towards the MC! It's what I felt make her romance more intriguing!

Now for Astarion I wouldn't mind having the option to either redeem him or not, I feel like it would be a complete slap in the face if things end badly for him as there are some parts to him that make him seem like he wants to be more chaotic neutral than chaotic evil.

Again I agree with what a lot of people are saying in regards to keeping him a villainous sadistic being,
But I want to be able to do that through choices, not through a set storyline, I feel like the MC should have an impact on the outcome of the companions somehow.
So I would love it if the way you make choices or the way you talk to Astarion could either make him become less "evil" or more.