Risa

At that point she's is not his daughter in the script itself. And he is not absurdly powerful as portrayed later by fans and prequels.

He's an angry evil space monk.

Oh that's 100% what it is. People complain about the Sequel Trilogy for 'not having a plan' but they also seem to be purposefully ignoring the fact that nothing in Star Wars was planned. The power levels for everyone are so stupidly inconsistent that you can't keep track. Vader is, in effect, a fucking God according to everything we've seen him in. With all the canon additions like Rebels, Jedi: Survivor, Kenobi, and all the comics we're seeing him at a power level thats, forgive the meme, over 9000.

Then A New Hope starts and he's a wet fish with no abilities at all and doesn't know how to swing a lightsaber. Kenobi says "Strike me down and i'll become more powerful than you can possibly imagine". Meanwhile that apparently translates to "I'll show up as a force ghost a couple of times and help in no way whatsoever". Yoda is a little grumpy gremlin in the Original Trilogy but is playing War Crimes Ping Pong in the Prequels/Clone Wars while being devastatingly powerful.

The writing for Star Wars just sucks because they keep focusing on the same 15 years before A New Hope. They've added so much to Canon that by the time you hit the Original Trilogy everything suddenly downgrades massively. At least Star Trek stayed consistent with its prequel stuff. Enterprise added a few extras, Discovery and Strange New Worlds expanded on some, but none of them created tech so stupidly powerful that it undoes everything in Trek after that point. You could argue the Spore Drive but at least Season 2 gives a solid reason as to why it never appeared in later Trek. There's no excuse for why Vader goes from someone who can force choke people in orbit to a dude who can't swing a fucking lightsaber without making it look like he's using 99% of his effort to move in that suit.