A Badass Boast involves a hero or villain using their achievements or power to command respect or fear. Yet among villains, it's common to command the same just by swearing to carry out some nefarious action.
This is distinguished from a regular threat by usually being aimed at someone other than the heroes they're speaking to. As with the quote above, the villain will sometimes swear to save the heroes for last after they're through terrorizing everyone else. All that matters is that the villain's not trying to get some kind of compliance out of their audience; they're shooting for an Oh, Crap! if they're not simply trying to pump themselves up.
This turns into Just Between You and Me when the bad guy starts giving away information that can be used against them.
- In Doflamingo's backstory in One Piece, he, along with his father and brother, were hanged on a wall and tortured by the mob for being former World Nobles (who oppressed those mobs, even though Doffy's family himself would never do that). Doffy, unfazed but angry, screams to the mobs' faces that he'll endure the torture and then he'll kill them all, one by one. The mob got taken aback by this.
- Green Lantern: Just as the Green Lantern Corps, the other Color Lanterns have their own oath to invoke the power of the Corps, specially Sinestro Corps, Red Lanterns and Black Lanterns are the most fitted to this trope, since these three factions are eviler than the other Corps, especially the latter Corps.
- The arch-nemesis of Marvel Comics' Fantastic Four, Doctor Doom, has made two solemn oaths: 1) to destroy Reed Richards and his teammates for having sabotaged Doom's college project (Reed did no such thing); and 2) free the soul of his Gypsy witch mother from the infernal realm. Doom has actually succeeded in the latter, having bested Mephisto and his hellish horde in combat (he had help).
- The Red Wizard Ommadon from Rankin/Bass Productions' The Flight of Dragons comes to the Temple of Eternity to meet with three other wizards to decide their course now that mankind is developing science to meet his needs. While the other wizards agree that an enclave realm of magic be created, Ommadon refuses to retreat to this "fools' paradise" and swears upon his red crown that he'll keep mankind fearful and trembling of his magical powers. Part of this effort includes Mind Control of heretofore docile dragons, converting them into Ommadon's Elite Mooks.
- The Swan Princess has Rothbart. Upon being banished from the kingdom, he vows that everything King William knows and loves will be his one day.
- Mission: Impossible III: Owen Davian gives one of these as soon as he wakes up tied to a chair, not caring one bit that Ethan Hunt and co. easily have the advantage over him for the moment.
"You have a wife, girlfriend? Because you know what I'm gonna do next? I'm gonna find her, whoever she is, I'm gonna find her and I'm gonna hurt her. I'm gonna make her bleed, and cry, and call out your name, and you're not going to be able to do shit, you know why? 'Cause you're gonna be this close to dead. And then I'm gonna kill you right in front of her."
- In Star Trek II: The Wrath of Khan, Khan copies Ahab's oath from Moby-Dick almost exactly when swearing to destroy Kirk, replacing the nautical/marine words with space ones.
- The legendary ghost ship Flying Dutchman has this in its backstory. While attempting to sail around the Cape of Good Hope in South Africa during a dangerous storm, the captain swears that he will never stop trying to round the Cape even if it means sailing until Judgment Day. The ship sinks, and its ghost and all the crew are indeed forced to sail until Judgement Day.
- Animorphs. The following quote establishes that this universe's version of Satan would rather spend its time slaughtering entire solar systems instead of killing the only being capable of standing a chance against it.
Crayak: I will cleanse this galaxy of all life. Then, when no sentient thing is left alive, I will kill you, Ellimist. That's my game. Shall we play?
- In His Dark Materials, Iofur Raknisson pledges, before fighting Iorek, that if he wins, he will hang his opponent's head and innards to the walls and make saying his name a capital felony.
- In Moby-Dick, Captain Ahab swears that he will kill the eponymous white whale Moby Dick at any cost, and will chase him to hell and back before he gives him up. It doesn't end well.
- In The Silmarillion, Feanor and his sons swear to regain the Silmarils at any cost, and to destroy anyone who impedes their goal. The supplementary work "The History of Middle-Earth" gives the full oath as follows:
"Be he foe or friend, be he foul or cleanElda or Maia or Aftercomer,Man yet unborn upon Middle-earth,Neither law, nor love, nor league of swords,Dread nor danger, not Doom itselfShall defend him from Feanor, and Feanor's kin,Whoso hideth or hoardeth, or in hand taketh,Finding keepeth or afar castethA Silmaril. This swear we all!Death we will deal him ere Day's ending,Woe unto world's end! Our word hear thou,Eru Allfather! To the everlastingDarkness doom us if our deed faileth!On the holy mountain hear in witnessand our vow remember,Manwe and Varda!"
- In the first book of A Series of Unfortunate Events, Count Olaf says: "I'll get my hands on your fortune even if it's the last thing I do!" It doesn't turn out well for anybody.
- Mostly seen in flashbacks, Slade Wilson in Arrow made a promise to Oliver Queen in the time they were stuck on the island after Shado was killed because of Oliver. Basically the "promise" is that he will come back to make him suffer and kills everyone he loves, including his mother, his sister and even their love interests, all of that becuase the death of Shado, which make him crazy, not just because of the Mirakuru in his system.
- The Book of Mormon, scripture of the LDS Church, has stories of these and warns against them. They are called "secret combinations" often overlapping with Deal with the Devil. Cain is said to have started it. It warns that they are found among every civilization, even in the modern era. Probably a reference that includes government and business corruption, and organized crime.
- In Bayonetta, the Big Bad we're introduced to in the penultimate chapter reels off a half-dozen of these across every cutscene he has screentime in.
- Following the final fight against the Masked Lumen in Bayonetta 2, he forces Bayonetta to her knees with sheer rage and swears on his soul that Loki will draw his last breath before him. Later chapters show us that, despite what he initially appears to be, he's more of an Anti-Villain.
- In War Craft III, Prince Arthas The Paladin makes what he thinks is a Heroic Vow to hunt down the demon general Mal'ganis, even to the end of the earth... however, it turns out that Mal'ganis was manipulating him all along to do so, and his rash vow made in anger is what leads to Arthas' fall, undeath, and, ultimately, transformation into the lich king.
- Adam from RWBY swore to Blake that he would destroy everything she loves as revenge for her betrayal.
- Doctor Dolittle (the Depatie-Freleng variant): The mobsters of D.O.P.I., led by one Sam Scurvy, invoke their "mean and icky" oath almost Once an Episode.
- Zordrak frequently made ones concerning his plan to invade the Sleeping World with nightmares in The Dreamstone. This didn't really stop it looking like a Felony Misdemeanor towards the heroes (who supplied No Holds Barred Beatdowns to his minions), so a later episode amped it. As the heroes were sneaking around his lair to get the dreamstone back, they overheard him devising his newer, far more menacing plans for it.
Zordrak: I shall take the Dreamstone to the Nightmare Planet and there I shall convert its powers to evil. I shall be unassailable. I shall be LORD OF THE UNIVERSE!!! ... None shall escape my wrath! ... I shall crush the Dream Maker and his minions with a single blow!