Board Thread:Questions and Answers/@comment-36950799-20190408203824/@comment-34974603-20190422220543

If you're on the Genocide Route, then you will be fighting Undyne the Undying. Make sure that you get the "But nobody came..." message before you fight her.

As for how many times you are going to die... It really depends on your reflexes and ability to think quickly. For me, it was like this: Imagine fighting normal Undyne. Now imagine the difficulty being multiplied by about three or four.

Hope that helped!