Follow the directions below to delete save games files from Disney Infinity games for Steam:

1. Log out of your Disney account. Go to the Main Menu, then "Options", "Online Options", and "Log out".
2. Close the game.
3. Right-click the game in the Steam Library.
4. Select "Delete Local Content", then "Delete" to confirm.
5. Exit Steam: go to "Steam" then "Quit Steam".
6. Delete the "Disney Interactive" folder in the App Data file.
7. Log back into Steam.
8. Reinstall and launch the game.

This will wipe everything except your DLC and Steam Achievements; they are linked to your Steam account.