The contacts stored on the OnePlus smartphone can be deleted from the Contacts app at any time.

This will delete all existing information or details, such as phone numbers, addresses, website entries or birthday.

If the contact is in the Google Account, the deletion will be synchronized immediately if the option is enabled.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Contacts app
Step 2:  Tap and hold a  contact
Step 3:  Choose more  contacts  if desired
Step 4:  Tap on  Delete
Step 5:  Confirm with  Delete
  1. Open the Contacts app
  2. Tap and hold a contact
  3. Choose more contacts if desired
  4. Tap on Delete
  5. Confirm with Delete

OnePlus Instructions