That's what I'm a bit confused on though - and maybe I just don't get it and that's okay too! But I feel like we don't see her get intentionally less gray - we just see lines she's not willing to cross. Narratively we're told RC was a turning point for her morally, but in both timelines she keeps operating in that system regardless. Then in 6, she goes through efforts of clearing her name, denounces her/bioterror work but then.... immediately goes back to it, keeping the same cycle she's been in since 2 even though the cleanest out she ever would have ever been presented was right there, if she truly detested it. Maybe I'm just taking redemption arc too literally.
Here's the thing though... we don't actually know that Ada keeps acting as an arm of that system. After RE4, and especially after RE6, it's unclear who Ada is working for and what she's doing. RE6 is her last appearance, and there is no clear indication of what she does after that.
Also, from a narrative point of view, the fact that we are shown more and more humanizing aspects of Ada's character is significant. Maybe there were always lines Ada wouldn't cross, but the way we are shown this starts to demonstrate a narrative. We are first introduced to Ada in RE2, where we see her as a character who is willing to betray Leon's trust and use him to steal a virus to sell on the black market, though we also see her demonstrate genuine care for Leon. Then in RE4, we see her betray Wesker to prevent him from carrying out a genocide, even though this act would anger Wesker, a very dangerous man, and taint Ada's credibility as a mercenary. Then in RE6, she is aligned with the heroes for the whole game; the only conflict is when she is mistaken for a clone who looks just like her. The decision to place these events in this order shows a trend of Ada increasingly shifting to the side of "good."
However, I also want to point out that good and evil is not always clear in this series. Leon works for the US government, which has been shown to be corrupt from the beginning of the series. The government contracted with Umbrella to develop BOWs. The government covered up what happened in Raccoon City. The government coerced Leon into being its servant to keep him quiet and contained. Simmons, a government actor, was the primary villain of RE6. The Connections, primary villains of RE9, are shown to have significant control in the US government. Leon and Sherry were operating outside the DSO, indicating that they are distrustful of the organization, even though it employs them. The point is, even though Leon is on the "good" side, he, like Ada, is working under a shady employer. The only difference being, Ada is more self aware about this than Leon and has been for decades.
I'm interested to see where her story goes. But I see Ada as someone who ultimately is moral and capable of moral actions. She just might go about it in different ways than Leon would, due to her experience and her more cynical nature. I see her becoming a jaded, pragmatic character, who works in the shadows with unclear motives but will come through when she needs to.
