"800-pound gorilla" is an American English expression for an entity so powerful that it can act without regard to the rights of others or the law.
[1] The phrase is rooted in a riddle joke: Q.
Anywhere it wants to.This highlights the disparity of power between the gorilla and ordinary humans.
The term can describe a powerful geopolitical and military force, or, in business, a powerful corporate entity that has such a large majority percentage of whatever market they compete within that they can use that strength to crush would-be competitors.
In law, the phrase occurs as a characterization of judges vs. courts; as in: "Standard/Court Rule" vs "Gorilla/Judge Rule".