Your Hosting Accounts/Addon Domains can be removed through the account's Control Panel with just a few clicks, however, please note, that your Hostinger profile cannot be fully removed for security reasons.
Access the Control Panel of the account you wish to remove and search for the Delete Account menu. You can use the Search Bar at the top of the Control Panel page to locate the menu more quickly.
IMPORTANT: Make sure to make Backups of the account you wish to remove to avoid any loss of files and previous hard work. When you Delete your account, your account's files and settings are removed from the server fully.