Is there a way to delete your account?

You can't delete your account. But sending a support ticket, by personal request they will permaban your account.

I don't believe so. I would trying messenging riot support.

Why delete it? Just don't login to it. Maybe in the future you decide, "Hey, I want to play some league." Regardless if you ever do or don't, you'll still have an account for either yourself, or a friend.