What is the Account name that you created ?
Name
This is the displayed name that people will see.
EDIT:
Sorry, I read this wrong at first thinking you wanted to delete an avast forum account.
For the newly created avast account, log-on to that my.avast.com account, open the Profile (Portrait icon or email link) that should give a drop down list > Profile Details. That should throw up another window and that has a Delete option.