How Delete Cloud Storage Data

[Doth]

Steam decided it wanted to save a broken version of a game onto itself, so now I need to reset my cloud storage to fix it. How do?

[Muppet among Puppets]

Disable cloud. Backup local savegame in case you change your mind.
Start game new.
Enable cloud. Choose the right save when notified.

[Jaunitta 🌸]

Rightclick that game in library> properties> updates tab > untick enable cloud sync remote storage.
Start game make a save then pause game enable remote storage while game is paused then when you exit game cloud sync will over write the last save.
Edit
you can play and save just fine without remote storage. All our saves are on our HDD for most of all games in our library just make a backup of them to a new folder with a description on a regular bases. Store on a USB external drive.
List of your cloud saves.
https://store.steampowered.com/account/remotestorage