Might Makes Right

Hey, at least he's fair.

"Good and evil are just words. Power always wins."
Dracula, to Trevor Belmont, Castlevania: Judgment

"I am stronger than you, therefore, I make all the rules."

This very simple aphorism can be used by a character of virtually any level of intelligence. Usually they're explicitly evil, usually. Bear in mind that anyone who espouses this belief will almost invariably be wrong - but the hero usually beats them by somehow being stronger than they are so, well, the Aesop is kind of broken.

Remember that physical strength is not necessarily the determinant here. Monetary wealth, political power, and just about any form of bullying can take the place of this. (Not that any professed adherent to this will necessarily admit it; the bully who uses physical strength may regard an ambush or other clever plan as cheating.)

Truth in Television for the vast majority of human history, including today. Fortunately for those of us living in Real Life, people who espouse this philosophy are not always explicitly evil; in fact, the whole idea of Knights In Shining Armor, True Warriors, and "Comes Great Responsibility" is to espouse and encourage the virtuous use of power. The truth is that "Might" is a weapon like any other: its effects depend on s/he who wields it. It is possible to use might for good.

War, however, is extremely expensive, both in terms of actual money and in terms of human lives, and tends to leave both sides the poorer for it, which is why people are generally encouraged to settle conflicts with something other than their fists. This is where the "violence is evil" underlying assumption comes from: someone who resorts to violence must be too stupid to use any of the more peaceful conflict-resolution tools. Or worse, are actively looking for any Pretext for War.

Of course, people and countries are often more than happy to use it as long as they're the ones with the power, but complain when it is applied to them.

Fictional characters taking this trope seriously can lead in all sorts of more specific directions:

Opposite hero trope:

See also Appeal to Force in Logical Fallacies. The Hedonist, when they are a powerful character, will usually use this logic. Related is Mutually Assured Destruction, when both sides are so powerful that peace is maintained precisely because both sides are too mighty to fight without destroying everything they were fighting for.