Me and my girlfriend pretty often have heated but respectful political discussions and recently we were discussing Stalin. She thinks that he was awful, mainly because of repressions, cult of personality etc.
When I say that repressions were actually good and Stalin didn't kill enough fuckers, she gets a little angry, but I can't seem to explain my position in great detail because of lack of knowledge.
In the case of the cult of personality, I say that Stalin WAS loved by the majority of soviet citizens because he did a shit ton of good for them, but she still doesn't quite get it.
What arguments would you suggest to use, or maybe something to read in order to deepen my knowledge on the topic?
My suggestion is to not get into extremely pointless historical relitigations with your partner over Stalin. Even if you knew what you were talking about, it would be a shame to tank your relationship over something that doesn't materially matter to either of you. As it is, you're repeating profoundly edgy memes to a comparatively normal person and then acting like it's their problem they are put off by it.
"Stalin didn't kill enough fuckers" is true, but mainly when you understand "fuckers" to mean "reactionaries imperiling the ML project" rather than just "people." There were many people, most notably during the "Great Purge," who were killed by the government and emphatically did not deserve it ("But it was Yezhov's fault!" true or not, you'd need to establish Ezovchina lore first.)
Someone else will probably handle the other aspects, but if no one does you can ping me