AccountKiller
Please follow the laborious instructions at the deletion link. This (probably) goes for player accounts only. The RS site account may be different. Heck, why not ask at their support address to delete it? That is: accounthelp@jagex.com.
Enlace de la terminación directa: http://services.runescape.com/m=rswiki/en/Account_deletion
Publicly visible text/images often aren't properly deleted even when you succeed in deleting an account. Try editing or deleting them manually before deleting the account itself. If you're unsure what happens to your tracks you can always contact RuneScape and ask personally. By the way, deletion requests don't necessarily mean your data will actually be deleted (e.g. due to legal obligations).
If you signed up for RuneScape using a third-party login such as Facebook or Twitter, you probably want to revoke all access from RuneScape. Click the icon below to find out how.