"But there is one they fear. In their tongue, he is Dovahkiin - Dragonborn!"
― The Elder Scrolls V: Skyrim
"In all my ambitions I never hoped to enter the ranks of Dragon Slayers."
― Boy Blue to Old Worm (Fables)
"He is a man who came from Wano Country in the New World!!! Believe it or not, a long time ago he was known as a legendary samurai who killed a dragon!!! And his story is still passed down to this day!!!"
― Dr. Hogback explaining Ryuma's origins to Nami, Usopp, and Tony Tony Chopper (One Piece)
True to his name, Dragon Slayer Ornstein (Dark Souls) has slain countless Everlasting Dragons with his signature lightning imbued Dragonslayer Spear.
As one of the Four Knights of Gwyn and the commander of the Dragonslayers, Hawkeye Gough (Dark Souls) used his Greatbow to shoot down numerous Everlasting Dragons from the sky during Gwyn's ancient war against them.
The Nameless King (Dark Souls 3) was a dragon-slaying god of war and the heir to lightning until he chooses to sacrifice everything by allying himself with the ancient dragons he once fought.
WarGreymon (Digimon) is equipped with Dramon Killers on each of its arms, which are weapons designed to kill beings with dragon attributes.
Boy Blue (Fables) killed the dragon Old Worm during his journey through the Homelands.
Grimmel the Grisly (How to Train Your Dragon: The Hidden World) is a merciless dragon slayer who believes that all dragons must be exterminated, having already hunted the Night Furies to near extinction by the time he first encounters Hiccup and Toothless.
After going insane from the loss of his dragon, King Galbatorix (The Inheritance Cycle) murdered every dragon in existence and their Riders.
A powerful samurai from the Wano Country of the New World, Ryuma (One Piece/Monsters) became a legend...
...for decapitating an enormous dragon with a single slash.
Wielding the legendary 21 O' Wazamono sword Shusui like his predecessor Ryuma, Roronoa Zoro (One Piece) decapitated and slew Dr. Vegapunk's artificially created dragon guardian of Punk Hazard.
Ragna the Reaper (Ragna Crimson)
Dragons can only be killed by Dragon-Killing Swords such as the Sword of Bruncvik (Supernatural) a special blade forged in the blood of a dragon by Eve to prevent the natural order between monsters and humans from being disrupted.
Buster Blader (Yu-Gi-Oh!) was designed by Yugi to counter Kaiba's Blue-Eyes White Dragon and so it gains more power for each dragon on the field or graveyard.