Subverted: Humans are fighting a war against an alien race, but try to establish peace talks.
Double Subverted: ...Only to unleash a surprise attack on the unsuspecting enemy.
A group of aliens are making a reality show, and in order to ensure a proper amount of conflict, turn to the most violent species they know... humans.
Only the the humans all turn on the guards, wipe them out, exterminate the crowd, then proceed to a bloody Gladiator Revolt and found an Empire of their own. All six of them. When they start inviting more humans from Earth to share in their good fortune all the aliens are so frightened that they have a heart attack.
Zig Zagged: At first, it seems that all humans do is fight with other races. But then, we see that those humans are actually a band of outcasts; the rest of humanity are pacifists. Unfortunately, the entirety of the pacifists are killed off, meaning that the warring humans are the only humans left.
Averted: Humans are not particularly violent.
Enforced: "How can we make humans Bad Ass?" "Let's make them always want to kick ass!!!"
Lampshaded: "Now, as ambassador of the Klingon-I mean, Human Federation..."
A politician from a conquered alien race cunningly convinces The Emperor to add to his glory by attacking a newly discovered race called...humans.
Defied: "Not all humans want to fight."
Humans' violent tendencies make other races avoid them, refusing all trade agreements with humans. Humanity's economy collapses.
The Humans are Genre Savvy enough to realize this trope and pretty soon they start a war of conquest through the universe, leaving much death and destruction behind them.
Reconstructed: The other races have respect for humans' resolve and battle prowess and know that it's much better to have humanity as a friend than an enemy.
Played For Laughs:
Although belligerent, human technology is so laughable that they come across as overeager kids rather than bloodthirsty warriors.
An alien invasion lands near a school and tries to Take Over the World. The chess-club geeks go over and brutally slaughter thousands of them in one hour. The jocks stand aside to let the geeks enjoy themselves. Then the geeks politely get out of the way and the jocks have their turn. The cheerleaders in the meantime swarm around the alien's flanks, grabbing a number of them and strangling them with their pom-poms. Someone suggests calling the police, but everyone agrees that, this would be unsporting and the whole school was enjoying the slaughter way to much to end it. Then the teacher decides that he has had enough of the aliens interrupting his class so he goes up to the alien army kills every one of the aliens personally and says to his students, "Ok you've had your fun, now get back to work. We have a test tomorrow."
Played For Drama:
The humans' war-mongering ways cause the other races to gang up against humanity, attempting to wipe all humans out once and for all.
Humanity's war-mongering ways cause all the other races to gang up against humanity, and humanity wins out through genocide.
Humans are known and respected by other races for their skill-at-arms and are prized as mercenaries.
Humans are the hatchet men for an alien Empire. Planet Terra is given favorable treatment in return for humans to keep the rest of The Empire in line.