The Worst Thing Zapp Brannigan Ever Did On Futurama
Few characters on TV are as indisputably unlikable as Zapp Brannigan (Billy West) from "Futurama." As a send-up of space captains of old like James T. Kirk (William Shatner) from "Star Trek," Zapp exhibits all the bad or unattractive qualities of early science fiction television heroes. He's ignorant, has an overinflated ego, and is incurably misogynistic. His first appearance in the series alone is defined by some very crass behavior toward Leela (Katey Sagal), and he once inadvertently killed his second in command before going on to sleep with his wife.
On top of that, Zapp doesn't much care for the livelihoods of the troops under his command. Heck, he won his fame as a military leader by needlessly sacrificing thousands of his men to a horde of rampaging killbots until they reached their preset kill limit and shut down. He's blown up the DOOP (kind of like the United Nations but in space) headquarters on accident, declared war on a planet defined by its unyielding neutrality, and sent ships manned by children on suicide missions. The point is, he is a bad guy. However, all of that (well, maybe most of it) pales in comparison to the worst thing Zapp Brannigan has ever done on "Futurama."
Zapp helped destroy chunks of the galaxy for Richard Nixon
As the main military leader of Earth, Zapp is ostensibly at the beck and call of its 100% "honest" president, Richard Nixon (Billy West). Granted, Zapp also sold out the last president to alien invaders, so that should tell you all you need to know about loyalty in the Earthican government. Regardless, so long as Zapp's safety is secured, he is willing to do anything for his superiors, and that includes protecting the interests of corporatists like Leo Wong (Billy West).
In the final "Futurama" film, "Into the Wild Green Yonder," Leo plans to wipe out an entire arm of the Milky Way to make room for his interstellar mini-golf course. As Nixon's biggest financial supporter, Leo has no problems getting Nixon to help him while he irreversibly damages the universe's ecosystem. When Leela, Leo's daughter Amy (Lauren Tom), and a few other notable female characters join together in an all-female eco-terrorist collective called the Feministas in order to oppose Leo's plan, Nixon sends Zapp to subdue them.
Zapp is successful in doing so, and Leo comes very close to getting his wish and imploding the all-important Violet Dwarf Star to create his course's 18th hole. Unbeknownst to him, the star is actually a massive alien egg containing the last known specimen of a benevolent race of godlike beings that collect the genetic information of the universe's endangered species for conservation. Had Fry (Billy West) not intervened, many species would have been lost forever.
Why this ranks as Zapp's worst atrocity
On the surface, it might seem like Zapp's actions here are greatly overshadowed by his previous atrocities. Because we usually value human life over anything else, it's understandable that playing a part in ruining the environment seems incomparable to outright killing thousands of people. However, in the long term, Zapp's role in "Into the Wild Green Yonder" does way more damage than simple mass murder.
Every planet and star system that Leo Wong destroys in pursuit of the ultimate mini-golf course is another potential wellspring of life that Zapp has a direct role in cutting off. This is not to mention the fact that blowing up the Violet Dwarf would condemn innumerable species to irreversible extinction. Zapp may have killed thousands of people with his bad leadership, but here he is actively killing millions of creatures and destroying thousands of habitable planets so that a rich businessman can play mini-golf poorly.
In addition, Zapp also wastes thousands of human lives in his pursuit of the Feministas. In one scene, his ship gets cut in half, and all but two of his men are sucked into the dark, cold void of space. Zapp responds to this by closing the ship's curtains and singing Duran Duran's "Hungry Like The Wolf" on their way to the repair station. In the end, Zapp is responsible for exponentially more deaths in "Into the Wild Green Yonder," both human and inhuman, than almost any other "Futurama" outing.