How to remove your Scratch account
1. Go to https://scratch.mit.edu/api/getinfobyusername/
After the / fill in your username. Find the numbers and copy them.
2. Navigate to https://scratch.mit.edu/users/close_account/
After the final / type in the numbers your account is closed.
(Thanks to Ed.)
Helpful Trick: Removing online data
Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact Scratch and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).
Helpful Trick: Remove third-party logins
If you signed up for Scratch using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Scratch. Click here to find out how.