Through time travel shenanigans, one character tries to kill their past self.
** = I love it, * = I like it , ^ = self-rec
Marvel Cinematic Universe
Thermotemporal Equations by Blinky the Tree Frog
T, Complete, >40,000
- Bucky Barnes is used to strange happenings; his time with the Howling Commandos has guaranteed that. He's therefore not totally thrown off balance when he wakes up in an extraordinary tower in a seemingly impossible year. He can’t help but be worried though, no matter how much reassurance he's getting from Steve and his new team.
* Weak Spot by grilledcheesing
T, Complete, >3,000
- Peter Parker has been sent back in time hundreds of times after their last face off with Thanos to do the one thing nobody else can: save Tony Stark.
Unfortunately, he has to find a way to kill his past self to do it.
And the last thing Tony is going to do is let him.
Supernatural
the easy way out and the hardest part by queenbaskerville
T, Complete, >3,000
- Sam would rather die than be Lucifer's vessel. Lucifer will just resurrect him now, but there was a time before the seals were broken—a time before Sam broke the seals. To save the world, to save Dean—Sam knows what he has to do.
It's not a baby, it's a timebomb by foolscapper
No rating, Complete, >1,000
- If you're still doing prompts I've been looking for fics where Sam goes back in time to when he was a child or baby to terminators himself. (A very difficult search unfortunately.) Whether he succeeds is up to you.
^ Monster by Rirren
T, Complete, >2,000
- Something has traveled back in time to kill 12-year-old Sam. Dean's not going to let that happen. But he might not need to kill this monster to stop it.
The Right Call by FictionalNutter
T, Complete, >4,000
- If Sam dies in the past, John won't be forced to sacrifice himself for Dean after a car accident, Dean won't go to Hell, and Lucifer's cage will stay shut.
Sam's family completely disagrees.
X-Men
By Any Means Necessary (Trial and Error Remix) by Unforgotten
T, Complete, Erik/Charles, >9,000
- After Charles' untimely death in the dark future, Magneto goes back instead of Logan—but no matter what he does to try to change the past, he can never seem to change himself. In the end, there's only one option left, and he's more than ruthless enough to take it.
Where There Are Still Gods by helens78
E, Complete, Erik/Charles, >1,000
- Erik comes from a broken world, eight years after a dark night in the water just outside Florida. He'll do anything to make sure that future doesn't come to pass.