Bo-Katan Kryze gets a Darth Vader moment straight out of The Empire Strikes Back in The Mandalorian season 2, episode 3, "Chapter 11 - The Heiress", so what does that mean for the character's future, and does it make her a villain? Having previously appeared in both Star Wars: The Clone Wars and Star Wars Rebels, Bo-Katan made her live-action debut in "The Heiress", for which she was the titular character, with Katee Sackhoff reprising the role.
Although not quite as well known in Star Wars as someone like Boba Fett, who returned in The Mandalorian season 2, episode 1, "The Marshal", Bo-Katan is still a big deal for the show: not only is she a proven great character in her own right, but she's one with ties to Ahsoka Tano (as touched upon in the installment) and to the deeper history and culture of the Mandalorians. Bo-Katan and her fellow Mandos - Koska Reeves and Axe Woves - ultimately work with Din Djarin, but there are clear differences in approach and how each faction sees what Mandalorians should be.
After Din helps Bo-Katan take the weapons from the Imperial ship, she then demands his assistance in fully taking control of it, as part of her quest to reclaim the Darksaber. When Mando objects and states that she is "changing the terms of the deal," Bo-Katan coldly and sarcastically replies with "this is the way." It's a very clear callback to The Empire Strikes Back, where Lando Calrissian reluctantly strikes a deal with Darth Vader, with the iconic villain stating that he is "altering the deal." The Mandalorian season 2, episode 3 is full of Star Wars Easter eggs (as the entire show is), and so it's hardly a surprise to see the reference in there, but it is interesting that it makes Bo-Katan, ostensibly a new hero, into the Vader of the deal-altering.
Bo-Katan is not a villain, as seen by the fact that she saves Mando several times and ultimately helps him find the Jedi in the end, telling him where Ahsoka is. At the same time, however, there's enough in the episode, including the Vader-esque scene, to highlight the difference in morality from the Mandalorians to, say, the Jedi, who tend to have a more black and white view on what is right and wrong. This also serves to better highlight the clear dissimilarities between Bo-Katan and Din: in season 2, episode 2, Frog Lady makes him remember the rules of the Mandalorian code, suggesting that following through on a deal is a must. Clearly, that isn't quite the case for Bo-Katan, since she changes the terms as she pleases, even if she does honor it in the end. The contrast between them was something the episode showed a lot, and the Vader reference makes it even more stark.
Bo-Katan's moral stance will likely be brought further into question when she returns in The Mandalorian season 2, since she is so hell-bent on getting the Darksaber back from Moff Gideon. The implication is that she will stop at nothing to do so and, while he's undoubtedly the villain of the piece, it will be interesting to see just how far she'll go, and what Mando will make of that, given the clear differences in viewpoints and codes between them. Bo-Katan may not be a villain, but she's someone who has suffered through a lot of wrongdoing to her people, and in her bid to lead them once again there will be sacrifices made and prices that need to be paid.