how do you delete your league account permanently

You can submit a support ticket and request it. You can also request it just be indefinitely suspended so you can get it back if you want to later.

https://support.riotgames.com/hc/en-us/articles/202647784-Account-Deletion-FAQ

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i want to delete this account i need your help

Go in game and make sexist/racist/anti-sjw remarks ;)

If that doesn't work...

just declare yourself to be "white" and not feel guilty.

its ur time to be toxic :D