You just need to follow these steps.
1. Go to mynextmatch.com and provide your login details to continue.
2. While in the lobby, click on the Profile Menu on the top right-hand side of your screen.
3. Click on Account Settings.
4. On the Account Settings page, scroll all the way down. Click on Delete Account.
5. Two new fields will appear where you will be prompted to enter an email address and your reason for deleting your account. The email that you enter will be the address that My Next Match will be sending your account details and data to.
Enter details and click Delete This Account.
6. You will view a information message in the screen.
Reminder: If you have at least one child account bound to yput account, you cannot send a delete request before a confirmation.