Self-explanatory. This information is not easily available.

Hi Gibson, I'm sorry to see that you want to leave the site. :[ 
 
You've already figured out how to delete comic accounts, but there's currently no way to delete a user account, probably because doing so would end up removing all the comments, forum posts, etc that person had made. The most I could do is freeze you, but I'm not sure what that would accomplish other than keep you from signing in again. You could do the same thing yourself by changing your e-mail address and password to something random.