Flowey is a character known through out Undertale. He is also an antagonist in The Neutral run. More about that later! 

He is a antagonist/protagonist in the no mercy run. He tends to remember times with chara. He speaks about his reaction to when he turned into a flower in the area called "New Home"

Chara is a close human child to Flowey, adopted by the Dreemurr's.

This is Asriel, Flowey's true form. He is fought in the true pacifist ending. He is chara's best friend.

Those are all the Flowey's in the game!

Flowey use's a weapon called "Friendliness Pellets" They are not so friendly to be exact. And then he says "In this world" "Its kill or be killed"