From the Super Mario Wiki, the Mario encyclopedia
Tenacious Tucks are members of the Snowmad army and enemies in Donkey Kong Country: Tropical Freeze. They resemble stout penguins wearing a protective helmet, as well as red striped trousers fastened around their body with a leather belt. Tenacious Tucks only appear during the third phase of the battle with Lord Fredrik, which takes place in Volcano Dome. In said battle, Tenacious Tucks, along with Tuff Fluffs, spawn from ice balls shot by Lord Fredrik's blowhorn.
Tenacious Tucks mix the qualities of both Tuff Tucks and Speedy Tucks. As soon as they land, the enemies begin strolling on the battle arena, charging into the Kongs when they spot them, much like Speedy Tucks do. Being protected by a helmet, they cannot be defeated with a jump attack, but will temporarily flip over and become inoffensive. In this state, Tenacious Tucks can be picked up and tossed into Lord Fredrik, who stirs around his throne in the background.