UNDERTALE/Flowey

Overview
Flowey is the first and only living being without a SOUL in UNDERTALE. He attempts to kill the player at the beginning of the game, before Toriel steps in and sends him flying. He then goes on to appear after Toriel's fight, and can sometimes be seen disappearing on certain maps when you go back to the beginning of that area. He is one of the main antagonists of the game, mainly in the Pacifist and Neutral routes.

Appearance
Flowey is literally a golden flower that has a face in the middle of it. He has the remarkable ability to imitate voices and faces and does so throughout the game. He imitates the player during the Neutral Route, Toriel during the Genocide and Neutral Routes, and Asriel (his former identity) before dying in the Genocide Route. He was created after a golden flower, injected with determination, was planted in Asgore's garden, where Asriel's ashes are.

Personality
He doesn't have a SOUL. How do you think he has a personality if he has no SOUL? Well, he does. He is very cruel and thinks the world is kill or be killed. He outright tries to kill the player after explaining this philosophy to the player at the beginning of the game. He also berates the player at the end of a Neutral route if the player has either aborted the Genocide route during the Neutral route or has reset during a previous Genocide route, asking why they were unable to finish the job. He does the same if you are on the Pacifist route, asking why you decided to start being nice.

After Toriel's Battle
Flowey appears after Toriel's battle and asks the player why they did what they did (unless the player is doing a Genocide route, in which case, he says he has a plan to make them all-powerful). Here are the exact quotes.

(If they have earned EXP)

 * Clever. Verrrryyy clever.
 * You think you're really smart, don't you?
 * In this world, it's kill or be killed.
 * So you were able to play by your own rules.
 * You spared the life of a single person.
 * Froggit, Whimsun. Vegetoid, Loox. Migosp, Moldsmal.
 * Think about those names.
 * Do you think any of those monsters have families?
 * Do you think any of them have friends?
 * Each one could have been someone else's Toriel.
 * Selfish brat.
 * Somebody is dead because of you.

(If they have not earned EXP)

 * Clever. Verrrryyy clever.
 * You think you're really smart, don't you?
 * In this world, it's kill or be killed.
 * So you were able to play by your own rules.
 * You spared the life of a single person.
 * Hee hee hee...
 * I bet you feel really great.
 * You didn't kill anybody this time.
 * But what will you do if you meet a relentless killer?
 * You'll die and you'll die and you'll die.
 * Until you tire of trying.
 * What will you do then?
 * Will you kill out of frustration?
 * Or will you give up entirely on this world...
 * ...and let ME inherit the power to control it?
 * I am the prince of this world's future.
 * Don't worry, my little monarch, my plan isn't regicide.
 * This is SO much more interesting.

(If the protagonist killed Toriel before)

 * Clever. Verrrryyy clever.
 * You think you're really smart, don't you?
 * In this world, it's kill or be killed.
 * So you were able to play by your own rules.
 * You spared the life of a single person.
 * Hee hee hee...
 * But don't act so cocky.
 * I know what you did.
 * You murdered her.
 * And then you went back, because you regretted it.
 * Ha ha ha ha...
 * You naive idiot.
 * Do you think you are the only one with that power?
 * The power to reshape the world...
 * Purely by your own determination.
 * The ability to play God!
 * The ability to "SAVE."
 * I thought I was the only one with that power. But...
 * I can't SAVE anymore.
 * Apparently YOUR desires for this world override MINE.
 * Well well.
 * Enjoy that power while you can.
 * I'll be watching.

(First time)

 * I hope you like your choice.
 * After all, it's not as if you can go back and change fate.
 * In this world, it's kill or be killed.
 * That old hag thought she could break the rules.
 * She tried so hard to save you humans.
 * But when it came down to it...
 * Hee hee...
 * SHE COULDN'T EVEN SAVE HERSELF.
 * WHAT AN IDIOT!!

(Second time)

 * Ha ha ha ha ha...
 * You disgusting animal.
 * You didn't even TRY to spare her.

(Subsequent times)

 * Wow, you really can't get enough.
 * You kind of remind me of myself.

(If Toriel was spared before)

 * Wow, you're utterly repulsive.
 * You spared her life...
 * Then you decided that just wasn't interesting enough for you.
 * So you murdered her just to see what would happen.
 * You killed her out of boredom.
 * Truly disgusting...
 * Ha ha ha ha...
 * You naive idiot.
 * Do you think you are the only one with that power?
 * The power to reshape the world...
 * Purely by your own determination.
 * The ability to play God!
 * The ability to "SAVE."
 * I thought I was the only one with that power. But...
 * I can't SAVE anymore.
 * Apparently YOUR desires for this world override MINE.
 * Well, well.
 * Enjoy that power while you can.
 * I'll be watching.

Flowey appears even if he was killed in a previous Neutral Route.
An audio clip then plays of Flowey exclaiming "Hmm...That's a wonderful idea!"
 * Hahaha...
 * You're not really human, are you?
 * No. You're empty inside. Just like me. In fact...
 * You're , right?
 * We're still inseperable, after all these years...
 * Listen. I have a plan to become all powerful.
 * Even more powerful than you and your stolen soul.
 * Let's destroy everything in this wretched world.
 * Everyone, everything in these worthless memories...
 * Let's turn 'em all to dust.

If Toriel Has Not Been Fought
Flowey's sound is heard repeatedly and dialogue box cannot be closed by "Z"
 * Error

Pacifist Route
He is seen in the beginning (duh) and at the end. If the player has befriended all monsters, seen the True Lab, and spared everyone, he absorbs the entire collection of the undergrounds monster SOULs (basically, he absorbs the soul of all the monsters you befriended), and returns to his true form Asriel. Asriel then introduces himself and battles the player. He can only be defeated by defeating the lost souls and by acting. He cannot be killed otherwise (unless you can hack).

Neutral Route
Flowey appears at the end and kills Asgore and his SOUL. He then absorbs the human souls and crashes the game. Opening the game again causes his battle as Photoshop Flowey to begin. He can then be spared or killed. Both cause the Neutral Route to end or continue as normal respectively.

Genocide Route
After killing Toriel, he sees you as Chara. He also tells his story as a flower in NEW HOME. And then he dies after he kills his former father.

Trivia

 * Flowey is the only monster or creature without a soul.
 * He is also the only monster that we know of who has come back to life
 * Naming the human Flowey causes the text, "I already CHOSE that name!" To appear, stopping you from using that name.
 * Flowey may be based off of the flower in Earthbound, which Toby Fox got inspiration from.