I'm not great at critiquing yet, but I'll do my best to give a fair review!

I like the handwriting and little illustrations that go with it because they look very... Non-threatening. The cute little happy faces, the little Christmas-y things like mistletoe and a bell, all of it looks very nice and happy just on its own and it really contrasts with the darker undertones in this picture (in a good way). The added "OR YOU WILL BE PUNISHED" in tiny writing is fun because it pokes fun at the whole "read the fine print" idea. The elf alone was drawn in a very interesting, more realistic art style. The way the irises in his eyes are drawn to look smaller really emphasize the fact that his eyes are bulging in horror and fear and the small details like the little shines on his gums and mouth really make it stick out. I also love that there's a little green light on his choker, implying that it's more of a pet collar than it is an accessory. You details for the fluff and hair are very consistent, making it stand out as a material without standing out so much that it looks like it's from a different art piece/style all together. I love that even though Santa isn't drawn in full detail, we all know who it is that's punishing the elf for not smiling just because of the little fuzzies at the ends of his sleeves. Making the fuzzy parts on the elf yellow instead of white was a great idea because since it's so different than Santa's, there's no questioning who's holding the candy canes. You also did a great job of using the red in a more ominous way, making it fade into a darker shade as if to imply that there truly is someone terrifying coming out from behind your elf. The only thing I can seem to fault you for was some of the blending. It looks a bit awkward on Santa's hands and some of the lighter parts kinda stick out as if they aren't actually a part of his hands. That's it, though.

Overall, you did a good job with combining dark and happy, by making the main message sound cheery while making the more obvious one a little more threatening. Amazing work. I'm sorry if this review was too long, but I hope it was useful!