The Monkey's Paw

Granted. You go through the same circumstances again with no knowledge of the "undo", make the same choices, get the same results that made you push the undo button in the first place, you push the button again, and you end up reliving the unpleasant experience for infinity in an endless loop - instead of moving on to something more pleasant.

Granted. It undoes exactly the action you want it to do, and overall works exactly like you want it to. But to keep reality consistent, it rewinds time for the whole universe. And every sentient creature is aware of what you're doing, but since the undo only works for you, they are forced to live through the rewound time every time you use it. You are not very popular.

Granted, but you don't have a redo option. Once you've undone something, you can never redo it.

Granted. You wake up one day and see a button at the corner of your vision. You think you're hallucinating but you're not. You concentrate on it and a debug menu appears which has all sorts of buttons: undo, redo, stop time, resume time, add money, add strength, set health to max, save, load etc.

It's great! In fact it's the best thing that could ever happen to you. You're free of your depressing life, you can do as you please, you have all the money, all the time, all the chances you could ever want, and you haven't even seen every option yet.

But after a few weeks it starts to dawn on you that this kind of thing should really be impossible. It's like it's straight from a video game. Are you living in a simulation? Is this a test? Is anything real?

The more you think about it the more depressed you get and the things that you enjoyed just days earlier seem meaningless. You explore this debug menu a bit more and you find something that you weren't expecting: the exit button.

As the days go by and you wake up every morning in your huge mansion with the worst hangover ever, you have had enough and you finally press is.

For a moment everything goes dark but then you wake up. Tubes and cables are sticking out of your body and you can barely walk. It's dark and cold, you look around and you see millions of other people hooked up in pods, just like you were. You start to make your way forward, trying to find a way to escape this hell, but it seems to go on for hundreds of kilometers, by your estimation. A few days later you die of dehydration.

Granted. But the button can get stuck when you press it.

Granted. The button undoes whatever you're thinking at the moment, whether it is your last action, your own name, or your beloved wife. You quickly realise you can't really control your thoughts.

Granted. Rick and Morty season 4 episode 8.

Granted. Every time you hit Undo your current timeline is destroyed, making you the most prolific mass murderer in the universe by a wide margin. A new timeline is created for you each time, but no matter what you try, each new timeline is slightly worse than the previous one, with your changed actiona only leading to worse consequences.

Granted. The button undoes the last 200 years if your life.

Granted. Whenever you press the button, your life will be undone.

I just respawn usually.

You go back a bit more then a single step because quantum autosave is only once every 5 minutes but still it beats living with every single mistake i make.

Big /S just in case, do not attempt this