UNDERTALE/Undyne

Overview
Undyne is a fish monster who is part of the Royal Guard. She is seen in the waterfall during all the routes and is initially very hard to defeat. She is even harder to beat on the Genocide Route.

Appearance
When Undyne is chasing the player before her fight, she is seen wearing armor similar to the Greater Dog's. She takes off the helmet of this suit when the player is about to battle her or when she seemingly corners the player before Monster Kid steps in. In the Genocide Route, she becomes Undyne the Undying, who has armor that is bigger and darker than that of Undyne's.

Personality
Undyne is brutal, harsh, and completely reckless. She shows this off during all routes, Genocide Route especially, when she battles the player and when befriending her. She can be nice, however, as she agreed to train Papyrus, even if he could never join the royal guard. In the Genocide Route and Neutral routes, she is seen to have Determination, despite it being impossible for a monster to have Determination. In the Genocide Route, this Determination transforms her into Undyne the Undying, while in the Neutral Route, it causes her to melt and die after a while. Not really that ideal, Undyne...

Pacifist Route
She is seen chasing the player and trying to kill them, you know that. But after you spare her by giving her water, you can hang out with her and start a Faux Battle with her. No matter if you Fake Hit or choose the Fight option, she knows somehow that you don't want to hurt her. Also, the attack deals one damage. So much for the Real Knife (not that you could get it this early in the game).

Neutral Route
You can fight or spare her. Sparing her causes at least 5 neutral route endings to occur depending on what else you did, while killing her can cause the Exiled Queen, Mettaton, Papyrus, or Doge Ending. It can also cause the Alphys and Leaderless Endings. The choice is yours. Should you start a genocide...

Genocide Route
You can't run, you can't hide, you can only kill the Undying Undyne. The fight is harder than the normal Undyne fight, so be ready. You should probably NOT do the Genocide Route because of this fight alone. And also, the Neutral and Pacifist routes (except for the Alphys ending) allow you to obtain the Temmie Armor, which would be useful for the Undying fight but unobtainable due to the Temmie shop replacing it during the Genocide Route. Also, in the Genocide Route, there is another fight that's even harder...

Trivia

 * Undyne may come from the name of a Greek water nymph named Undine. Coincidence? I think not.
 * If the player calls Undyne after talking to the royal guards, she says that she showed them an animation of humans controlling minds during the war. She goes on to say her hands are tied because the guards have been told that if Undyne says to let a human pass then she was being mind controlled.
 * When Undyne was younger, she followed Gerson around to watch him beat up bad guys. She ended up "beating up the mailman or something like that."
 * Undyne and Toriel are the only bosses that the protagonist can flee from during a battle on a Neutral Route.
 * Undyne's battle can only be fled from if the protagonist's SOUL is red, however.