What about Darth Vader becoming creepily obsessed with the new young senator from Alderaan who reminds him remarkably of his late beloved wife? And Palpatine picks up on the obsession and makes Vader escort her to events and serve as a bodyguard when there's a threat of assassins (sent by Palpatine, probably), so that Vader wonders if it's all a little bit of history repeating.

He stalks her and sends her terrible gifts (e.g., the severed heads of her enemies) and watches surveillance video of her sleeping, because he is a giant creeper.

There is a ton of gossip around the Senate about it and Leia is like, "could this situation possibly get any more horrifying?"

And then they find out she's his daughter, so the answer to that is yes, yes it could.

Bonus points for Vader's self-loathing kicking into high gear and maybe turning him into a double agent to try to make up to Leia for this, but even he must know there's some forms of creepy you just can't come back from.