Time travel in fiction is a tricky thing. It's hard to do properly without breaking the established rules and without being so riddled with plot holes so big that you could drive a bus through them. I'm a big fan of the concept of time travel and the possibilities story wise. Heck, my favourite show is Doctor Who, a series so muddled by its own rules and canon that some episodes completely contract each other when it comes to the rules and the consequences of breaking them. Fixed points in time can't be changed...except when they can. What happens when a fixed point is changed? Reapers try to fix the tear in time and space- except when time just slightly changes with little very consequence... but sometimes all of time and space collapses and just happens all at once.
Hell, the video game Life is Strange broke its own rules before the rules were even established. Throughout the game the main character Max can rewind time to change events but when she does this she doesn't psychically move backwards as well. She could go into a room, rewind time and she would still be the room, effectively teleporting as well as time travelling. You have to actually use this feature to work out a puzzle so it's canon... but at the start of the game Max rewinds with everyone the first time she uses her powers. It's not like it's something she has to practice to achieve. After that first time she can just rewind time while popping up in front of people randomly (not that anyone comments on this for some reason...)
I could go on for ages on plot holes in time travel fiction but that's not the purpose of this post. I tend to overthink things and time travel is no exception. At the end of Back to the Future we see Marty watching himself go back in time to (presumedly) go through the events of the film, only for Our Marty to wake up in a completely changed timeline where everything he did changed his entire family's lives. This is the same timeline the other Marty has lived in all his life. This is obvious because the Twin Pine Mall is now the Lone Pine Mall. So I asked myself, what happens to the other Marty? He didn't grow up on the story of how his grandfather hit his dad with the car. Instead he grew up on the story on how his parents' friend, Calvin Klein, pushed him out of the way. So it makes sense to me that he follows George, sees his dad is about to get hit by a car and does nothing- because he doesn't think he needs to. He expects "Calvin Klein" to rush out and push George. So George gets hit by a car, resetting the timeline and when he goes back to the future he arrives in Original Marty's crappy life. The two Marty's literally swap lives.
Recently I was browsing Netflix when I came across When We First Met. It wasn't like I had anything else to do (plus I'm cool with watching anything with Shelley Hennig), so I gave it a shot. It wasn't an amazing film but I did enjoy it. It did, however, get me thinking. The main character Noah keeps resetting time to ty and win the girl of his dreams by changing his approach, only to wake up three years later to find that each time everything has gone wrong. He tries again and again until he eventually achieves his goal...only to realise that it's all wrong and he needs to put everything back to normal. With each reset he ends up talking to his crush's best friend, Carrie, reevaluating his life and what he wants while also learning more about her and eventually falling for her. It was a bit predictable but harmless- or was it? Throughout the film he grows closer to her through experiences that, for her, never happened. It never happened because Noah kept resetting the timeline but we see that from each new version of the timeline that the characters had lives. I know it's a weird thing to say because it's obvious but from Carrie Version 3's point of view, Noah announces he has to go back and fix everything and shortly after she ceases to exist. He literally wipes her from existence. He basically murders her and everyone else in the world multiple times until he fixes everything.
Sure, time travel stories usually brings up that time travel can wipe someone from history or prevent people from being born. About Time did it...even though when you think about it the logic behind the reasoning doesn't make sense. The Doctor Who episode, The Girl Who Waited, literally points this out. An alternative version of Amy points out that by changing the timeline that she would be erased and she doesn't want that to happen. Whenever a piece of fiction does point out a character will be wiped from existence it's always one of the main characters but we never think about the other people in that timeline who could be erased.
So it turns out that many of our time travelling heroes might really be mass murderers...