Deleting part of the game’s data is a very bad idea, as generally a game does not expect this behavior and could have undefined results.

If you want to delete your saved progress in a game, it is best to find a way to do it from within the game. Most games (at least should) allow a way to delete progress or start new. If it does not, then you could bring it up to the developer.

The only exception I can think is if a game explicitly mentions what the save file is, or even better prompts the user to select where to save the progress in their filesystem (outside the game folder). That usually hints that the save file is not dependent to the rest of the game and can be deleted without issues.