How to remove your Mint account
From their help pages:
1. Login to your Mint.com account.
2. Click on the Your Profile link at the top of the page.
3. Click the Settings icon in the toolbar of the window that opens.
4. Scroll to the bottom of the page and click the red link to Delete Your Mint Account.
5. Click YES, delete my Mint Account.
6. Type your password to confirm, and then click on Finish.
7. The confirmation box will appear stating that your account has been removed and the confirmation email will be sent to you shortly. Click OK.
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for Mint using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Mint. Click here to find out how.