Chris Cringle a.k.a. Santa Claus, as played as screen icon Mel Gibson, is not really "fat" as the title would imply, but Mel makes the character a badass. However, Chris has incurred the wrath of a thoroughly repugnant devil-child. Billy Wenan (Chance Hurstfield) is a rich 12 year old child whose nasty actions have motivated Chris to gift the kid with a lump of coal. But the kid retaliates by calling upon his favorite hitman (the great character actor Walton Goggins), and hiring him to assassinate Chris!
"Fatman" was, for this viewer, an ingeniously twisted little tale that works hard to be edgy, and delivers some good dark comedy. Of course, it's far from being for all tastes, especially as we see that Billy is ready and willing to torture a schoolmate when she wins a science fair first prize that he feels should have been his. Fairly grim (but not overwhelmingly so), and very violent, the film also delivers some unexpected poignancy as Chris bemoans the state of the world today - and the bad attitudes of its children. Chris himself has fallen on such hard times that he enters into a temporary partnership with the U. S. military, where the elves will be making product other than toys.
Mel is in fine form, and he and the wonderful Marianne Jean-Baptiste make for a rather endearing Mr. And Mrs. Claus. Goggins is superb as the icy-cold, super-efficient hired killer who has his own reasons for wanting to bump off St. Nick. (One amusing character trait is that "Skinny Man"s' pet of choice is a hamster.) Young Hurstfield is very, very good at creating a child character so despicable that you hate him from the word go.
In general, whatever problems the movie has are made up for by the entertaining story that provides an off-the-beaten path experience for those viewers who may be tired of "feel good" fare.
Eight out of 10.