On a computer that is fully synchronised with Football Manager's Cloud saves from Steam/MS Store/Xbox app/Epic, go to Load or Save game and select the 'Cloud' tab.
Here will be listed all your saves on the cloud. Select a save game and then click the 'delete' button to remove them from the cloud.
You must have an active Internet connection to use the Cloud Save Settings.
You can also manually remove them by visiting the following location for Steam and Epic:
Steam: C:\Users\YOUR WINDOWS USERNAME\AppData\Local\Sports Interactive\[Football Manager title]\cloud\games
Epic: C:\Users\YOUR WINDOWS USERNAME\AppData\Local\Sports Interactive\[Football Manager]\epic_cloud\games
If nothing above works, please submit a support request stating exactly what you've tried so far, and a member of our team will try to help.