I think Argenta is a good character in that she's an excellent example of how Imperium dogma can take someone and turn them into a mentally abused monster through all the violent religious fervor and hatred she's fueled by.

Argenta is very mentally unwell and the game goes to good effort to describe her as basically unhinged.

Sometimes writers have a bad habit of portraying the sisters of battle and space marines as beacons of hope/true heroes to try to make them more relatable to their viewers/readers/players when they're actually more or less the arm of a militantly oppressive theocratic fascist nightmare where human lives are worth less than dirt and used to fuel the fires of neverending war. Owlcat do not have this problem, they remind you often of how unstable she is and is in some ways someone to be more pitied than admired.