Antagonist: If my ideology is enacted, everything will be better!
Liberal Protagonists: oh fuck how will we deal with this, I have no arguments to defend the status quo
Antagonist: just kidding, all that ideology was a trick, I’m Just Evil™
And then they can kill him without thinking about anything at all. Happens all the time.
Off the top of my head is legend of korra (I know im 2 weeks late for that discourse) the Black Panther movie, and even Pokemon Black/White have the same themes
To be fair, sometimes it goes:
Antagonist: My ideology is a fantasy version of eugenics!
Liberal Protagonists: oh fuck how will we deal with this, I have no arguments.
Then the protagonist kills the antagonist and a million nerds on the internet talk for years about how the antagonist was actually right.