iCloud storage fail when trying to reset games
If you reset the iCloud data and the game data persists, you have likely discovered the game vendor is storing your game data and just linking it to the app install or to your AppleID / account.

The best place for help would be the vendor or a second question listing precisely what app you are using, what version of that app and what steps you take to clear iCloud - if other devices are syncing data, removing data on one device might not remove it from the cloud / other devices.