What's your least favourite trope, and can you think of any time it actually worked?
"The Dark Side Will Make You Forget"
To me, it's the single worst trope in the world. The idea that a nebulous "magic" will just turn you into an evil person is one of the most pitiful storytelling tools I've ever seen. It's a self-serving fantasy that serves to implicitly tell the reader that their evil actions are not their fault.
Lord of the Rings came close to doing this trope in an interesting way, and given it was one of the first that makes sense. The Rings of Power aren't just power that corrupts you because of Ambition Disease, they were a literal trap set by Sauron who lied about their powers. They were designed specifically to dominate and control their wearers. It was a scam. And people who knew about the Rings knew they were a trap. They knew that though there was a temptation to wield Sauron's weapons against him, that's exactly what Sauron wanted them to do.
It puts the onus less on the magic itself and on the ego. That such a trap can be so brazenly advertised and it's consequences well known means that only a complete and total fool would actually think they can resist it. So many people thought they could resist the Ring's corruption, but the Ring itself wasn't the thing you had to worry about.
Shadow of War is probably the best version of that, because Talion puts on Isildur's ring knowing full well it will eventually dominate him. He accepts that the moment he puts it on, resolving to resist as long as he can to hold back Mordor. In that end, it's not a foolish ego trip, it's just a really sad self-sacrifice.
In truth, despite it being the one to create the trope, Lord of the Rings doesn't really do "The Dark Side Will Make You Forget." It doesn't make you forget. You're being dominated and controlled.
The Silmarillion on the other hand RELISHES in this trope. Sauron's entire backstory is "I was good, but then Morgoth shook his ass at me and then I was evil because of... reasons."
Where this trope doesn't work is when it tries to do this with natural, benign powers like Fel Magic, or the Dark Side of the Force. There's no reason for this turn you completely evil unless you were already the kind of person who would be inclined toward evil in the first place, and yet it so often does anyway because writing characters having their own personality failings that led them to evil might hit too close to home.
It's like that fallacy "Power Corrupts." No it doesn't. You were already corrupt. That's why you wanted the power in the first place. And that's the part people don't want to accept.
