Gamma Hunters are bioweapons made by the Umbrella Corporation. They are 8 foot tall bipedal amphibian monsters with large claws, a huge, toothless frog-like mouth, but no visable eyes. Likely using thermal vision and strong hearing to catch their prey. 
Gamma hunters are gluttonous creatures. They prefer to weaken their prey before swallowing them whole. Even if the prey isn't actually dead yet.
They don't speak human language. They croak like frogs to communicate with other Gamma Hunters.