By allowing Snow to live, however briefly, she's making the statement that she's not the only person those in power need to worry about anymore. Katniss has done her part, and the rest of the population has already been galvanized by her taking a stand.
Control: As the leader of Panem, President Snow wanted to maintain his power and control over the districts. Katniss became a symbol of rebellion and hope for many people, which threatened Snow's authority.
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.
Coin had stolen his political power, using Katniss and her military arsenal for that purpose. Snow was NOT an honest man, but in this case, him telling Katniss the truth was out of a desire to get revenge on Coin, pushing Katniss to kill her.
He is portrayed as a villain, but his ultimate goal is to maintain peace and stability in Panem. Snow recognizes the threat of rebellion and the potential for chaos if the districts were to gain too much power.
What if Katniss Killed Snow Instead of Coin (Hunger Games Theory/ Fan Fiction)
Why does Coriolanus Snow turn evil?
In the end, Spruce and Sejanus are hanged at the Hanging Tree; Snow feels responsible for Sejanus' death and is wracked with grief. According to Jacobson, Sejanus' death is a "defining moment" that is "essential" to Snow's transformation into the evil President Snow fans know from the original trilogy.
During his time spent with Lucy Gray Baird, Snow gives into his evil impulses by telling himself that all of humanity is just as dangerous as he - the propaganda spread by the Capitol. By revealing this backstory, Ballad of Songbirds & Snakes will prove Snow was a despicable villain from the time he was a teenager.
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.
Although she will never know for sure, Katniss does recognize that she cannot be with Gale. She will never be able to forgive him for his idea — the parachute bombs — that killed Prim.
Alma Coin was the true villain of The Hunger Games, with Katniss actually seeing her as more of a threat than Coriolanus Snow. At the same time, it was Snow who was made out to be the bad guy in previous movies, making some question why Katniss killed Coin and spared him.
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.
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.
She was also against the games itself, whilst Snow believed the Districts were below him and continued working to implement new aspects of the games. Their relationship was so undesirable that Snow fired Tigris as a stylist personally.
It was here that Snow first heard the mockingjays, taking up the tune after the jabberjays repeated Chance's last words, "Run, Lil, Run!" He took an instant dislike to the birds, an unnatural muttation of the Capitol-bred jabberjays.
Gale does not marry anyone in The Hunger Games. He and Katniss talk about running away together and starting a new life in the wilderness, but they never officially marry.
Gale was responsible for creating weapons that would trigger a second wave of bombs to target first responders and combat healers. This invention potentially ended up killing Prim, but even if he wasn't directly responsible, Katniss found this tactic so abhorrent that she lost her affection for him.
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.
This comes as a result of Lucy attempting to leave Snow during a rainstorm after they plot to flee the Districts, but she learns that he was responsible for killing Sejanus Plinth during the travels.
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.
In the end, Katniss and Gale grew apart, as many childhood friends and young loves do. She needed something different in her life, and with Gale's link to Primrose's death, Katniss found a reason to cut ties. If Katniss ever wanted to find comfort again, she knew she had to return to Peeta for the long term.
Snow was 18 during the 10th Hunger Games, making him 8 when the first Hunger Games took place. This means that during the 74th Hunger Games, he was indeed 82 (74+8). So he died at 83 in "The Mockingjay," since that was during the 75th Hunger Games...
Unknown to most people, President Snow poisoned others but drank the same drink as them to cover up his tracks, resulting in perpetual blood sores in his mouth. The scent of these sores are covered up by the signature white roses he is always seen carrying.
Lucy Gray was also the first and only female victor from District 12 until Katniss won the 74th Hunger Games. While the 10th Hunger Games were long forgotten, Lucy Gray's spirit lived on in District 12 and Katniss specifically.
