https://dc.fandom.com/wiki/Action_Comics_Vol_1_512

I've been reading Silver and Bronze Age Superman this year - up to 1980, and I come across this disturbing story.
In a convoluted plot, Lex murders a terminally ill woman in cold blood (I believe this is the first time Earth 1 Lex has actually killed someone?) and replaced her with a clone, altered so that when she kisses Superman she and Superman will be exiled permanently into an anti matter universe.
Lex brainwashes himself to forget about his plan and to believe he genuinely wants to be good. He cures the rare disease killing Angela (or her clone anyways), he and Angela fall in love, Lex gets a pardon and becomes Superman's new BFF (sorry Jimmy) and marries Angela, the clone (which makes him a bigamist since he still has a wife on Lexor).
Superman kisses Angela at the wedding but super speeds away so he isn't transported to the anti matter universe with her. It took a couple of readings for me to figure out that I think Superman was just on his guard and able to escape, and didn't actually know what would happen to Angela. It's pretty tragic and haunting to know she was left there. Lex killing an innocent woman in cold blood really pushes his villainy to the next level, beyond redemption imo. That's an issue as the novel Miracle Monday, set in Earth 1 continuity a year later, says that Lex and Superman will be friends again in the future.
It's worth pointing out that Lex created a Superman clone back in Action 500, who got depowered and then was never mentioned or seen again. It seems like a missed opportunity to do something else with that character.