You can delete the message. You can’t delete the fact that they already read it.

Deleting removes the evidence and leaves the event. Whatever they read is already in their head doing whatever it was going to do, and a vanished message often makes it worse, because now there is a gap where the words were and the imagination fills it. The button undoes the record, not the reading.

When you send something you regret, skip the delete and go straight to the repair. Say you were angry, say what you actually meant, and let them respond. Trying to make it disappear tells them you cared more about the trace than about them.