Dallis is the tragic villain of DOS:2. She's the classical trope of "i'm a villain because i've been hurt and y'all gonna suffer for it".
And the tragedy is. The other way was just right there. She didn't meet the right persons, thus she was denied of it. She cannot evolve past her Eternal point of view - and we know how Eternals may think of mortals, see Fane, see the whole "let the Eternals come back" ending. She sees mortals as vermin, and she's ready to wipe them out if necessary ( the battle on Lady Vengeance where she let Vredeman kill grusomely most of the Seekers is a good example ). She hates the Eternals, she hates the God King, but she's still a product of this culture.
While Fane. Fane who is an Eternal all the same. Fane who, when we first met him, wanted to bring his people back so they may "have [their] world again", who sees you as an useless and retarded creature. This same Fane who, much later on, can't bring himself to doom this world so his own can come back. This same Fane who sees now the beauty of this world, and that it is worth living. This is because of the Godwoken. Because Fane met the Godwoken at the most convenient time, and this band of heroic losers show him, in their own way, how beautiful this world can be, even in this void-tainted state.
Who does Dallis meet, when she's free from her prison ? A poor woman whom she steals the face, and then - Lucian. A man whose motto is probably "the ends justify the means", the one responsible of a genocide for the "greater good", the one that wasn't afraid to kill tens of Godwoken to achieve his goal. So, at his contact, Dallis learnt nothing - how could she learn the value of mortal life when the very Divine saw those as disposable ? And she may think she was equal to him, but she was another tool of violence in the Divine's hands. Hence the way he talks to her :
Dallis, control yourself. Our purpose transcends your personal wounds.
Her only motivation, vengeance, is depicted by Lucian as lesser and, i can also note the AUDACITY of resuming thousands years of prison and the destruction of her own world as mere "personal wounds". And she obeyed. She obeyed him ! Anger is a violent feeling, and one can be manipulable when this anger became wrath, and Dallis seems to be consumed by it. Lucian was here to offer her vengeance, he was the promise to satiate her rage and so, she strode all Rivellon in his name to kill the ones coming through his way.
Lucian lost his lapdog when Ifan became a Lone Wolf, he'd found another in Dallis.
And this is very unfair, because in the end, Dallis was just a scared little girl, who was left to rot in a tomb, because dad thought knowledge was better than his family's safety. And he was gifted another chance - he met the godwoken, and he saw the mortal world as a place of beauty and wonder. Not Dallis : Dallis, wrongly imprisoned only saw the world through Lucian's eyes : filled with violence and death.
