Talk:Sans/In Battle/@comment-29670640-20160817192419/@comment-27701762-20160817193003

At some point or other you did not complete the requirements for the Genocide Route. Your run would have certainly been aborted prior to facing Undyne, as you face Undyne the Undying as a replacement for normal Undyne (and the change is quite apparent).

You will need to start over from the beginning. Make sure to grind out every single possible encounter in each area before facing the boss of the area. So start in the Ruins and just keep getting random encounters until you get an encounter that says "But nobody came." Once you see that message, you can move on to face the boss.

To make it go faster, hold Up+Down to wallhump against a wall (don't press left or right while doing this), and once you've killed a monster, leave the room and return to make the step counter reset. Otherwise you'll likely be waiting for 5-10 minutes for the last few encounters.