Only the Owner profile (the first account used to sign in and access the device) can remove an account.
From a Home screen, navigate: Apps > Settings > Users (Device section).
From the Users and profiles section (located on the right), tap the Trashcan icon located to the right of the corresponding user.
For restricted accounts, tap Settings icon > Trashcan icon (located in the upper-right).
Tap DELETE to confirm.
This removes the user's space and data from the device. The action can't be undone.