What do I need to do to start over from scratch with Grim Dawn? To erase all stats, achievments and previous loot . How do I delete or erase cloud saves for Grim Dawn?

I don't use the cloud, but maybe this thread would help

http://www.grimdawn.com/forums/showthread.php?t=20752

Move your saves from GOG's cloud system to local saves and then delete the local save folder. That will wipe all your characters and loot, including the transfer stash. No idea if you can delete achievements once you've earned them.