There is NO happy ending.

Clue number one - "Krampus comes to take , not to give. " Common sense should tell you, Krampus would not GIVE them a second chance. Max's chance, was to go on, without his family. He didnt accept the gift, and rather than take the offer he wanted to join his family (he was allowed to join his family, but now the way he wanted to)

Clue number two - The scared look on everyones faces , replaying the voices of the previous night. All of them realize the horror is real.

Clue number three - The final scene is in a dreamy atmosphere. It seems to be one of the "old Christmastimes" that Max dreamed about. Pretty eery for a family who just 24 hours ago, couldnt get along .

Clue number four - Snow globe. Snow globes are beautiful, but also haunting because the world inside them never changes. They are captured inside of one, forever. Meaning, their lives are in a standstill. They will repeat the same Christmas for all eternity.

Clue number 5 - Krampus intended to leave Max alive . Allowing the family to have a happy ending was never in his plans.Nothing about his behavior before the final "happy" scene , including the sinister laughing and throwing Max into the fire pit, says that he intended to spare or have mercy on anyone

And..finally, the camera zooms out to show us many snow globes. Critical thinking would lead you to believe that those are the snow globes, of other families, trapped forever in limbo.Those snow globes dont represent second chances, they represent "worlds" with people trapped inside them. There are a lot of other unfortunate souls and families dead, but alive, inside of those snow globes.

The end.