Really Gnawty is a giant Gnawty who is the boss of Gorilla Glacier in Really Gnawty Rampage in the game of Donkey Kong Country and is also known as the fourth boss in the game. Really Gnawty's name is a pun on "really naughty", similar to Very Gnawty's name being a pun on "very naughty".
Although Donkey Kong or Diddy Kong only need to jump on Really Gnawty five times to defeat him (just like Very Gnawty), this beaver boss is more difficult than the previous one. Not only does Really Gnawty horizontally jump even faster and farther than Very Gnawty (and he gets even faster and farther with each hit as well), Really Gnawty can also jump extremely high vertically. Once Really Gnawty gets hit, he makes a surprised expression. Then, he laughs and jumps high in the air, attempting to crush the Kongs from above, and he adds another high jump for each additional hit.
In the Game Boy Advance remake, Really Gnawty is recolored blue and is larger than in the original game. In the remake, when Really Gnawty is jumped on, instead of jumping at the Kongs, Really Gnawty jumps to the other side of the arena once, causing stalactites to fall to the ground.
- Really Gnawty is a palette swap of Very Gnawty. While Really Gnawty has brown fur, Very Gnawty has gray fur. In the Game Boy Advance port, this is reversed, though like all Gnawties, Really Gnawty's fur became blue instead of gray.
- Gnawties equal in size to Really Gnawty appear in Donkey Kong 64, near Cranky's Lab in Jungle Japes. The only difference between Really Gnawty and these Gnawties is that the large Gnawties of Donkey Kong 64 can be defeated in just one hit, rather than five as in Donkey Kong Country.