After all, she had technically betrayed the current government since the public wasn't aware of why Katniss would kill President Coin. However, Katniss killing President Coin was necessary to ensure that Katniss, the Capitol, and the 13 Districts were liberated from the fascist government 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.
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.
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.
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.
President Alma Coin is the main antagonist of Mockingjay, the final novel of The Hunger Games trilogy. She is the president of District 13 and is very corrupt and in some ways worse than President Coriolanus Snow.
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.
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.
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.
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.
Did Gale mean to kill Prim? No, Gale did not mean to kill prim but he still designed the bomb. But, although he holds a small fraction of responsibility, he never meant for Prim to get hurt.
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.
Did Paylor know about Coin? When Katniss emerges, Paylor asks her, "Did you find what you were looking for?", and Katniss holds up a rose, which Paylor takes as an affirmative response. This seems to imply that Paylor was somehow aware of Coin's betrayal and wanted Katniss to find out.
Katniss also realizes that, even though Gale had nothing directly to do with Prim's death, the bombing trap that killed her was based on one of his designs, which makes both him and Katniss feel he is somewhat responsible.
President Alma Coin's proposal, exposing her villainous nature. President Alma Coin is the main antagonist of Mockingjay, the final novel in The Hunger Games trilogy and both of its 2014 and 2015 film adaptations, The Hunger Games: Mockingjay – Part 1 and The Hunger Games: Mockingjay - Part 2.
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.
According to the star behind Effie, Elizabeth Banks, she and Haymitch's Woody Harrelson improvised the scene. Considering she's been adamant about the characters having some romantic connection, it only makes sense that they'd share a goodbye kiss. It's very on-brand for Effie, as well.
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.
At an unknown point in time years before the 74th Hunger Games, she was personally fired by Snow, the stated reason being due to her being too surgically enhanced.
On their journey, Snow lets it slip that he previously killed three people, making Lucy Gray suspicious, since she only knew about two. Jacobson says that the moment is a major shift in Snow and Lucy Gray's relationship as they rationalize the bad things they have done in different ways.
Katniss blamed Gale for the death of Prim. She would never be able to look at him again without thinking of his part in her death. Gale was the best friend he could have been to her at that moment. He knew her so perfectly to understand this, he knew his chance with her had passed.
Katniss Everdeen: As an evil, ruthless, and calculating dictator, Snow doesn't have many close relationships in The Hunger Games trilogy. His most important relationship is with Katniss, and it's one that's marked by hatred on both their parts, though they swear to always tell each other the truth.
He grows up in D12 with the Covey, and eventually at the age of 24 in what would be year 36 he gets married and has a baby boy born in year 37. That baby turns out to be Katniss's father. He gets married in year 57 and Katniss is born in year 58. So Snow could be Katniss's great grandfather.
