The five year debate about Palpatine's return in The Rise of Skywalker was reignited after Ian McDiarmid brought it up in Empire's recent interviews for the prequel's 25th anniversary. It's a tired debate, and has been pretty much since it gets started. But one particularly common argument that keeps bugging me is that Palpatine's return somehow negates Anakin's sacrifice. And like with my defensiveness over the "Rey Skywalker" ending, I have to defend this movie. This is all a matter of opinions, of course, and you can feel however you want to about it- but I just don't think that Palpatine's return does anything to negate Anakin's sacrifice.
The biggest element to this is, in my mind, the fact that I don't think Anakin's sacrifice was about Palpatine at all. Sure, ending his tyranny and the first big step of the Empire's fall was a nice bonus, but that is not what Anakin was trying to do. In that moment, I don't think he cared about Palpatine, or the Empire, or the Rebellion, or the whole galaxy. That moment, that choice, was all about Luke. It was about saving his son when he was in danger, and showing Luke that he was right to still believe in him. If just giving Palpy a big hug was what was needed to save Luke's life, then that's what he would've done, because offing Palpatine was just a side effect.
Anakin's final act in Return of the Jedi is, undoubtedly, the act of a Jedi. That is how it's clearly been framed since 1983. And act of hatred, or an act of revenge towards Palpatine is not the act of a Jedi. But an act of compassion is. Anakin's compassion for his son is all that matters when it comes to this sacrifice, and through Luke going on to do good in the galaxy, his sacrifice is fulfilled. And nothing, not even Palpatine, can undo that.