Katniss and President Coin didn't get along during their time in District 1, with Coin not believing that Katniss had what it took to lead a rebellion. Coin appeared to be a fervent supporter of the Rebellion, but she took advantage of the movement to further her own political interests.
Snow laughs after Katniss killed Coin because he enjoys the irony of the situation. He avoided the official execution ceremony, even though Panem's citizens still take their revenge on him, while Katniss ends up snatching away the victory and power that Coin thinks she has successfully secured.
She personally assigned Peeta to join the squad despite the fact that his hijacking had brainwashed him into trying to kill Katniss. This was presumably an attempt on Coin's part to dispose of the girl amid the battle, making her a martyr and preventing her from becoming a threat to Coin's authority after the war.
It is still possible that she genuinely wants to make Panem a better place, but her methods become inhumane. Coin feels threatened by Katniss' rebellious nature. In the end, her own delusional idea of Panem is her undoing, since she ignorantly trusts that Katniss is okay with her being the new president of Panem.
In The Hunger Games series, Katniss killing President Coin instead of President Snow surprised many. Still, it was because Coin was revealed to be a ruthless leader with her own political interests.
Katniss speculates that Coin deliberately sent Prim to die in the Capitol bombing in order to fully gain her trust, but it's never outright confirmed or denied.
Using knowledge from the movie and the books, let's break down how The Hunger Games ends. Coin killed Prim to destroy Katniss because, as Boggs (Mahershala Ali) explains before his death, Katniss is her biggest threat to maintaining her power over Panem because of the influence Katniss has over the people.
It is likely that he is a relative of Hilarius Heavensbee. In the Mockingjay - Part 2, Plutarch appears to smile as he looks at Coin's dead body, suggesting that he approved of her death.
Answer and Explanation: Prim is killed by a bomb at the very end of the battle. Alma Coin sees an opportunity to turn the Capitol troops against Snow, and she decides the resulting loss of life from her plan is a worthwhile price to pay.
By killing Coin, Katniss ensured a chance for a peaceful and fair country, avenged her sister's death, and liberated Panem from the fascist government. The Hunger Games franchise is still an iconic series of books and movies, with the latter truly cementing the property as an international phenomenon.
After reading the book and watching the film, it seems clear that Lucy Gray realizes Snow was responsible for the death of his friend Sejanus Plinth (Josh Andrés Rivera). If Snow could sell his best friend down the river for personal gain, it was only a matter of time until he did the same with her.
Peeta decides, though, that he will go out on his own to act as a diversion in case Katniss and the others need it. Gale gives Peeta his nightlock pill in case Peeta's captured. They leave early in the morning, bundled up and styled by Tigris. Cressida and Pollux go first, leading the way to the City Circle.
That said, it was stated that an emergency election took place after Katniss assassinated Coin. Commander Paylor, a vital leader in the Second Rebellion from District 8 was elected as Panem's new president.
Katniss searches his eyes for signs of emotion but only finds amusement in them. She remembers that they did indeed promise not to lie to each other anymore, and she realizes that Snow wasn't lying to her about Coin's role in the parachute bombing.
Before the Capitol battle, Gale had explained to Katniss his series of bombs designed to feed off human compassion: a small bomb would go off, and then when medical aid rushed in, a second bomb would go off, killing those people as well. Incidentally, it's this exact type of bomb that took Prim's life.
By killing President Coin, Katniss risked her safety in order to not only avenge Prim's death but also gift the people in Panem a chance to live in a peaceful and fair country for everyone. Katniss was incarcerated for a time, and she was sent back to District 12 after she was deemed unsuitable for a trial.
To put it short and simply, Prim's death is a message from Suzanne Collins telling us all that children can and do also die in war. In war, you can't protect even the most innocent and vulnerable because war and destruction don't discriminate.
Snow can't stand to see a young woman betray a young man's affection—his view of what happened 65 years ago. And so he takes out his old, festering wound on Katniss.
Boggs reveals that Coin had wanted to save Peeta from the arena instead of Katniss. Katniss represents a threat to Coin, and Katniss made the situation worse by forcing Coin to rescue the other victors. Boggs reminds Katniss that she has outlived her usefulness to Coin.
Katniss's focus on survival and her family's safety prevented her from fully considering romance, but her feelings for Peeta and Gale diverged in the end. Katniss ultimately chose Peeta because he understood her trauma and she didn't want to lose him, proving her love for him.
Katniss feels betrayed, most of all by Haymitch, who used her and Peeta. Eventually she wakes to find Gale there. He's badly injured and tells her the Capitol bombed District 12 after the Games. He got Prim and Katniss's mother out in time, but the District 12 is gone.
In the 74th Hunger Games, Clove was the only Career tribute who came close to killing Katniss twice — at the Bloodbath and at the Feast, and certainly seemed to have a deep hatred for her, perhaps because Katniss received a higher score than her.
