Basilisk

A basilisk is one of those things that is so incredibly scary that people (in universe) may not have fully thought it through. While a basilisk may be an apex predator, when emplaced/employed by a witch or wizard, it is only really useful as part of an ambush. The fact that Riddle kills all the roosters in Chamber of Secrets¹ tends to confirm non-magical legends that the sound of a crow's cry is fatal to it.² If you take that as true, then anyone who 1) knows there is a basilisk around and 2) has any time to prepare can defeat the snake fairly trivially. This remains true even if a transfigured rooster is not sufficiently real to cause the desired effect.