The added user accounts can be deleted at any time by the owner or administrator of the OnePlus smartphone.

All data and apps of the respective user account will be irrevocably deleted.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  System
Step 3:  Tap on  Multiple users
Step 4:  Open the  Settings
Step 5:  Tap on  Delete user
Step 6:  Confirm with  Delete
  1. Open the Settings
  2. Tap on System
  3. Tap on Multiple users
  4. Open the Settings
  5. Tap on Delete user
  6. Confirm with Delete

OnePlus Instructions