What is a mammal that tough when cornered and has two black eyes feeds on nearly everything it can catch in the pond?

The mammal you're describing is likely a mink.

Here's why:

* Tough when cornered: Minks are known for being fierce and aggressive when threatened. They have sharp teeth and claws and will fight back with incredible strength.

* Two black eyes: Minks have dark, almost black eyes.

* Feeds on nearly everything it can catch in the pond: Minks are opportunistic carnivores and will eat a wide variety of prey, including fish, frogs, crayfish, snakes, and even small mammals.

Let me know if you have any other clues!