The https://askubuntu.com/help/deleting-account shows wrong information. I am looking for a real way to remove my account from this site.
It's not wrong, there is no delete option for you because you voted and or posted, the next line is
If you have voted or posted, please contact the Stack Exchange Team:
Visit the contact form and select 'I need to delete my user profile.' After you contact us, the team will reach out with further instructions.
Just click the contact form link and go to 'I need to delete my user profile.', this is how you remove your account.