Dynamax Articuno

Dynamax Articuno has a relatively defensive stat spread, so it makes a good tank, right?

Well... no. Articuno is cursed with two major issues for a tank: first, its lack of a 0.5 second Fast Move, meaning it's pretty slow at generating energy for Max Guard, Max Spirit, and damage-dealing Max Moves for its team. Second, it's an Ice Type... which is objectively one of the worst defensive types in the game. Seriously; if there's even a risk of something carrying any type of Rock Type move, it's best to leave it on the bench. Sure, it does have a few resistances like Ground and Grass that could work in its favor, but on the whole it's better to use other options that can fill this same niche and do so better.