Last season is the last, so despite them setting up Kim as a darker character, they don't have time for her to go fully "bad", when it took Walter White 5 seasons to do so.
Definitely a more interesting development than simply setting her up as the moral compass for Jimmy and leave her like that.
Also Lalo is thought to be alive in BB, so he still may end this show with some clout, considering the Salamanca still boss people around in BB. 
Walt is a meth dealing murderer in Season 1 lol
Also Kim's "breaking bad" has happened the entire series (although I think that's always a rather reductive view of BB/BCS either way.)
Loved this season.
I mean it's true, he's technically dealing meth and has killed, but he only kills two people in (more or less) self defence, a far cry from all he does after that, when his reasoning to hurt others is essentially entirely ego.
Not to justify his early decisions, but the metamorphosis of Walt's persona happens through his internal interpretation & rationalization of his amoral actions, more than just the actions themselves, which necessarily took much longer than one season.
As for them setting up Kim to go "bad" from the start, while Walt's direction was incredibly obvious from the beginning, i think hers has been very ambivalent, up to the latter half of this season.
Yes, she has been craving Jimmy's lure for misbehavior, but her catalyst for exploding into that part of herself, wasn't really there like it was for Walt (with his cancer excuse).
Arguably any character (or person) has potential to end up on both sides of the line, but Kim's trajectory has never been that obvious or straight, in my opinion.
She's not mentioned in BB, so of course there's only so many ways you can get rid of her, but if she did go to prison for something like what they're planning to do to Howard, it wouldn't have been a "Saul never talkes to her again" bad moment.
Although maybe she's in some federal prison, and Saul did talk to her on the phone off screen.

Short of killing her, i'm not sure how you can break the two, now that she's down in the dirt with Jimmy, and you can't just rely on the classic "never talk to me again" thing.
