Talk:Undyne/In Battle/@comment-26577623-20160705174227/@comment-28988480-20160710170144

Undyne appears to be the only monster in the game to naturally produce a power known as "Determination". However, a monster's body is unable to keep up with that kind of power, causing it to melt sooner or later. In her last moments, Undyne clings to life via Determination. Thus, she melts some turns later.

In Genocide Run, Undyne's Determination seems to empower her body so much that it becomes strong enough to handle it, transforming her into "Undyne the Undying".