You were fighting the royal guard.. Undyne, you’d fought hard, you were determined to escape her while still being pacifist. You tried your hardest. But..

It was too late, she struck a spear right through your chest, you fell to your knees and start to choke blood, a loud ring in your ear, spots in your vision.

She stood over you, staring down at you, you saw a flash of regret in her eyes, behind her helmet, it almost looked like.. guilt..