its because the capitol hijacked his memories and its makes him hate katniss.
The Capitol hijacked Peeta's memory about Katniss and is supposed to think she is his enemy and has to kill her.
Well, if you read the books, you know Peeta loves Katniss. Katniss loves him and Gale. They knew it would hurt her beyond measure to see him go from her gentle lover, to a raving insane person who wanted to kill her at any time.
Peeta is mad because Katniss's love was fake.
. . .
Throughout the whole 74th Hunger Games, Peeta thought Katniss's performance of love she made for him was real, but it wasn't. Katniss's love was just an act she put on to please the Capitol audience and live. Peeta, however, felt much more for Katniss than just friendship and was very down when he found out nothing that happened in the arena had been real.
Katniss's suspicions started the moment Peeta asked Haymitch to train separately from Katniss, and grew stronger when she discovered Peeta had joined the Career Tributes, and finally overhearing them talk about Peeta leading them to her.
Katniss thought that Petta was dead because he wasn't breathing.
In The Hunger Games Katniss shoves Peea into a flower pot because she's mad at him for embarassing her by anouncing his love for her on public television.
SPOILER: Yes.
Katniss Everdeen-Stay with me.Peeta Mellark-Always.Mockingjay, page 314
there are five but the two main ones are katniss and Peeta
As seen in the epilogue of Mockingjay, she has had two children with Peeta, who she selected. Gale works for the government after the abolishment of the Hunger Games.
He tries to kill Katniss after the Capital brainwashes him in Mockingjay.
at the end of mockingjay both peeta and katniss get married and have two kids.
In a tweet, Suzanne Collins said their names are Willow and Rye.
Katniss Everdeen
SPOILER: Yes.
Katniss, Peeta, Gale, and Haymitch
peeta gave bread to katniss when they were 12 and katniss and prim and their mom were starving
Neither of them die.
Katniss Everdeen, and Peeta Mellark
Katniss Everdeen-Stay with me.Peeta Mellark-Always.Mockingjay, page 314
Peeta Mellark.
there are five but the two main ones are katniss and Peeta
peeta mellark lives in district 12 with katniss everdeen