There have already been games that have played around with the "moving backwards from end to start and trying not to cause time paradoxes" mechanic (see Retro/Grade, for example, or even my own game qmuHS, hint hint), but Spoiler Alert does a nice job of adding to that rather small pile.

It's a platformer in which you start from the last boss, and must then rewind back through the game, unkilling enemies and uncollecting coins. There are some neat twists and turns along the way, and it's all very zany and silly, as you might expect from a Tinybuild-published game. Out now on Steam.