Kong's chest looks pretty great for somebody who was shot to oblivion with machine guns and had open heart surgery. Not even a scar.
When the rednecks pour beer into Kong's mouth, he only has a sip. When he spits the beer back out, it's way more than he actually has in his mouth.
In the transplant scene, the blood spatter on Dr. Amy Franklin's mask changes between shots.
In the beginning, we hear Kong's heart beating. We don't hear his heart beating at any other point in the movie, even during the quiet scenes.
Some times when Kong walks, it makes a "thud" and the entire ground shakes, and other times, it does not.
The incision that the doctors make to perform Kong's heart transplant is totally wrong.
Kong eats alligators and later a man. Gorillas are herbivores and not carnivores. He could've survived on surrounding vegetation. Not accurate.
It is stated that Kong could not survive in the wild, without finding a sufficient source of protein. Actual gorillas' diets consist of mostly vegetation, and are very low in protein. However, this is a fictional film in which artistic license has been taken. Kong is an entirely fictional creation, not a true gorilla, and therefore can eat whatever the filmmakers say he can.
The nerve gas is enough to knock out a 50 foot gorilla, yet, seems to not affect humans. Many of the soldiers take their gas masks off, even while the gas is still visibly present in the air, and are unaffected.
When Kong frees lady Kong from the net, you can tell that it is precut.
When Kong first sees the alligator, it is a full-grown adult alligator. When Kong picks up the alligator, you can tell it is just a baby.
Don't make sense when Kong is trapped by the hunters and snaps a man in two but eats the other one.