i heard that when undyne tells you to deliver a letter after you beat flowey you are locked into true pacifist and you can kill monsters without ending the run
well there's no monsters to kill.
-Encounters have stopped because you spared every boss
-The only amalgamate you can damage is Snowdrake's Mother, and she regenerates every turn
-You can't kill Asriel, and I don't think you can kill the Lost Souls