The Mean One

During Christmas Eve in the town of Newville, a green humanoid being dressed in a Santa Claus suit attempts to rob the Christmas decorations from the home of a young girl named Cindy. She stumbles upon the creature and gives him a necklace until her mother attempts to fight him. In the struggle, the creature accidentally pushes Cindy's mother against a nail that pierces her neck, killing her. Before the creature escapes, Cindy calls him a "monster", angering the creature.
Twenty years later, Cindy returns to Newville for closure and to spend Christmas with her father, Lou. She bonds with police officer Burke Goldman and reunites with Newville's sheriff Peter Hooper, who continues to dismiss Cindy's claim of her mother's murderer being a monster due to lack of evidence. He reveals that Newville stopped selling or putting up Christmas decorations after the incident. That night, Lou finds old Christmas decorations and puts them up with Cindy. While she is taking out the trash, the creature locks her out and kills Lou before stealing their decorations.
Cindy later wakes up in the hospital, where she meets Newville's mayor Margie McBean, who is uncomfortable with Cindy's claims of the creature, believing it will cause panic. After her father's funeral, Cindy finds a rare flower in her home and traces it to a mountain via a website. Cindy finds the wallet of a missing person and sees the creature killing a couple before retreating. Shortly after, Hooper tells Cindy he cannot investigate as the mountain is in federal territory, although Burke agrees to help. Meanwhile, the creature slaughters a group of Santa cosplayers in a local bar.
As the creature attempts to break into Cindy's home, he is scared off by a man known as Doc Zeuss, who believes Cindy's story since his wife was murdered by the creature years ago. Burke goes to the mountain and finds the creature's hideout with several wallets of missing people. Cindy trains and prepares to kill the creature, who rampages through Newville and kills several residents. Burke discourages Cindy from facing the creature and finds out the wallets all belonged to tourists who were lured to the mountain by the same website Cindy saw, which is owned by Mayor McBean. He confronts Hooper, who confirms the creature's existence and explains that after Cindy's mother's death, the creature returned every Christmas to slaughter more people, and later his hideout was found. Hooper and Mayor McBean collaborated to make the website and send unsuspecting tourists as sacrifices in order to stop the creature's killing spree in addition to removing all Christmas decorations from the town.
Mayor McBean attempts to leave the town, but the creature kills her on the way. Burke heads to the mountain to kill the creature but becomes injured and is rescued by Cindy, Hooper, and Doc. Hooper goes after the creature but is killed. Cindy retreats to her decorated home and waits for the creature. When the creature arrives, she ambushes and engages him in a fight. Cindy finally incapacitates the creature, but before she can kill him, Cindy sees that he is still wearing the necklace she gave him twenty years ago. Realizing that the creature never wanted to hurt anyone and that his murderous behavior sparked only when she called him a "monster", Cindy forgives the creature and kisses him on the cheek. This act of kindness causes the creature's heart to grow three sizes, which ends up exploding and kills him. Sometime after, Newville reverts to displaying Christmas ornaments, the creature is deemed an urban legend, causing the town to become a popular tourist destination while Cindy and Burke start a romantic relationship.