The user can kill a deity/deities or any divine embodiment they may choose to get rid of. They are resistant to the effects of a deity and are capable of killing the specified deity. The user may be a deity with vast or corrupting powers or a being higher than a deity. Because deities are powerful and numerous, it may require instigating a war to kill them all at once.
The Monado (Xenoblade Chronicles); via The True Monado
Asura (Asura's Wrath) was not only able to slay the Seven Deities, but was even able to kill Chakravartan, the creator of the Universe.
The Hunter (Bloodborne) was able to kill several Great Ones - Lovecraftian Gods worshiped by the people of Yharnam - with nothing but brute force.
The Chosen Undead (Dark Souls) was able to slay a pantheon of gods with nothing but his/her shield and a sword.
Lucifer Morningstar (DC Comics/Vertigo) is so powerful that he would be able to kill pagan gods and members of the Endless if he chose to.
Titus (DC Comics) is an alien being of immense power who came to Earth in an attempt to challenge and kill its Gods, something he claimed to have done on numerous other worlds.
After becoming one with the Universe Seed, Hearts (Dragon Ball Heroes) became the Ultimate Godslayer...
...wielding the power to easily erase Fused Zamasu, an immortal god, from existence.
Chelia Blendy (Fairy Tail) is a Sky God Slayer, bestowed with the power to heal from injuries and the power to kill a god.
Orga Nanagear (Fairy Tail) is a Lightning God Slayer, one bestowed with the power to kill a god.
Kratos (God of War) was destined to be the downfall of Olympus. Because of this, Zeus betrayed him and sent Kratos on a path of vengeance and desolation all aimed at the Gods.
A hero of the Trojan War, Diomedes (Greek Mythology) was capable of wounding gods, driving Aphrodite and Ares away in fear for their lives.
Han Sung-Gong's (Hardcore Leveling Warrior) personal attribute, Oedipus, grants him the ability to kill his father and God of Lucid Adventure, Han Gun-Jae.
Zero (Hardcore Leveling Warrior) summoning God killing weapons via her skill, The Rain of God Annihilation.
Shinbu (Kingdom of Paradise) is a powerful warrior who was able to master all five Sword and Chi Arts of the Five Clans, then learned the San'Yuan in its purest state killing Genbu, Suzaku, Byakko, Seiryu, and Banko.
Hanzo's Armor (Kubo and the Two Strings) - when joined together - is powerful enough to slay Kubo's grandfather the Moon King.
Azrael's Blade (Lucifer) is a weapon powerful enough to kill and eradicate the souls of angels and possibly the Goddess of creation.
The Demorgorge/Atum (Marvel Comics) has power that makes deities seem human by comparison.
Gorr the God Butcher (Marvel Comics) is a mortal who wields All-Black the Necrosword, capable of killing gods and gaining strength from their blood, becoming powerful enough to easily defeat sky fathers.
The Sentry (Marvel Comics) brutally kills Ares, the God of War.
Ryu Hayabusa (Ninja Gaiden) is a ninja of the Dragon Lineage. Although he his human, he possesses connections to philosophical and spiritual arts. Due to this, Ryu is able to push past his physical limitations, allowing him to defeat supernatural beings and even supreme deities.
The Olympian Crystal (Once Upon a Time) is so powerful that it is the only thing that could kill a God.
Satanael (Persona 5) was able to kill Yaldabaoth, the God of Control, in a single hit of its Sinful Shell.
In addition to his both monstrous strength, Shiba Kyouichi (Shinmai Maou no Keiyakusha) is a user of "Ars Decidium", a special combat form that focuses on the art of killing high-level gods and demons alike.
As an Archangel, Lucifer (Supernatural) can kill or destroy entities like pagan deities....
...and angels like Castiel with ease.
Scathach (TYPe-MOON) possesses the God Slayer skill.
Gilgamesh (Valkyrie Crusade) is a murderous deity that kills other gods, being know as the god-slayer.
Goetia's (Valkyrie Crusade) fire can burn virtually anything, even gods, to ash.
Longinus (Valkyrie Crusade) wields the holy spear Longinus, that can destroy deities.
Ragnarok (Valkyrie Crusade) is a WMD that can kill deities.
Xena's (Xena: Warrior Princess) second pregnancy endowed her with the power to destroy Zeus and the Olympic pantheon.