"I taught you before. In order to control people, you have to exploit the darkness in their hearts. If there is no darkness, then you just have to create it. You never thought I would also use the same trick on you."
― Madara Uchiha to Obito Uchiha (Naruto)
" I always like to have reminders around that there is no good he can do... that I cannot corrupt."
― Mister Negative (Marvel Comics)
"Do you think if you hold back just enough, you won’t succumb, that you’ll leave this fight the same as you entered? Look to my example, boy! There is no resisting the Mark or the Blade. There is only remission and relapse! My story began when I killed my brother, and that’s where your story inevitably will end."
― Cain to his descendant, Dean Winchester (Supernatural)
"How does it feel? Horrible, isn't it? But, wonderful, yes? *laughter* Who you were before is insignificant, who you are now is inconceivable. But here, you shall remain, 'till I have need of you again... for one must always reign... beneath... DUSK! *maniacal laughter*"
― Nyarlathotep, after corrupting Dusk Dude. (New Blood Interactive's DUSK)
"The malice of one evil person is like an epidemic, the spread of its influence could do far worse than just hurting and killing a lot of people. It could even give rise to another evil by destroying the innocence of another victim by hurting and tormenting them too far, driving them into madness. Sometimes, the victim can turn into a far more horrifying evil than the progenitor responsible for creating it."
The user can use the ability to corrupt a person into doing anything. It does not control the victim, but it prevents them from realizing what they would, otherwise, not do as the user suggests. Therefore, they become much more malleable. The user needs a small amount of proximity and contact to corrupt someone. This proximity or contact is needed occasionally to prolong the effect.
It is easier to corrupt someone to do something minor (e.g., more corruption would be needed from the user to get a victim to murder someone than to steal.) Others can break the corruption, but it is not easy and would usually need outside influence. An example of an ability that others could use to break the effects of corruption is Belief Inducement. If the corruption is not renewed by the user occasionally, it will eventually wear away on its own accord.
Corrupt even the most good-hearted of people.
Make a person do evil things that they wouldn't otherwise do on their own.
Infernal Cup (The Mortal Instruments); induces Conversion to turn Shadowhunters
Orochimaru's Juinjutsu (Naruto)
Star Forge (Star Wars Legends)
Mayhem Mirror (Thea Stilton: The Magic of the Mirror)
The Seal of Orichalcos (Yu-Gi-Oh)
Roger's Golden Turd (American Dad!) can corrupt people that see it with greed to the point that they'll kill friends and loved ones.
Calvin Dion Avericci (Archie's Weird Mysteries) used special gift cards to corrupt teenagers into shopaholics, which in turn allowed him to turn them into mannequins.
In addition to giving its user incredible power and increasing their power, the Scrolls of Forbidden Spinjitzu (Lego Ninjago: Masters of Spinjitzu) also induces aggression and corruption, seemingly causing the user to become addicted to it from prolonged usage until they turn evil.
The powers of the three Oni Masks (Lego Ninjago: Masters of Spinjitzu) resurrected and corrupted Lord Garmadon.
Experiment 624 "Angel" (Lilo & Stitch)
Mister Negative (Marvel Comics) can corrupt people with his touch, the effects being more prominent the more good his victims have in them...
...with Spider-Man, a hero through and through, being reduced to a menacing, murderous villain who shuns all of his old values, including the memory of his Uncle Ben.
With the power of the Butterfly/Moth Miraculous, Hawk Moth (Miraculous: Tales of Ladybug & Cat Noir) can turn normal butterflies into akuma...
...which can turn normal civilians into supervillains.
Discord (My Little Pony series), was able to corrupt Twilight's friends, bringing out the worst of their personalities.
Alicorn Amulet (My Little Pony: Friendship is Magic)
After being sneezed on by Aku, Jack (Samurai Jack) was slowly corrupted into a clone of Aku.
Malefor (Skylanders) is able to corrupt others and transform them into loyal servants.
Sonic's Mech Suit (Sonic Boom)
Following his death on Mustafar, Lord Momin's (Star Wars) essence inhabited his mask, corrupting the minds of anyone exposed to it through the dark side of the Force.
The Corrupting Light (Steven Universe) was a weapon utilized by the Great Diamond Authority to corrupt the remaining Gems on Earth.
Red Kryptonite (DC Comics) alters Kryptonians minds by gradually destroying their inhibitions turning them into a corrupt version of themself; without any morality, compassion, rationality, or care whatsoever, become hostile and aggressive, making them a danger to everyone around them, or in other words, bringing out every negative thought to the surface.
The Chaos Pearls (Randy Cunningham: 9th Grade Ninja) have tainted essence that grants, it's users like The Sorcerer to have the power to taint others, turning students into monsters, making him even more powerful the the chaos the stank students spread.
The One Ring (The Lord of the Rings) is an incredibly powerful magical artifact that grants invisibility to those who wear it but has a corrupting effect on anyone who even looks at it.
Freddy Krueger (A Nightmare on Elm Street)
Emperor Sheev Palpatine/Darth Sidious (Star Wars) corrupted Anakin Skywalker and several other Jedi to the dark side.
The Mark of Cain (Supernatural) slowly corrupts the bearer until they become bloodthirsty killers. Upon their death, it corrupts their soul into a demon. It is even powerful enough to corrupt Archangels, such as Lucifer.
Rabids (Supernatural) are humans that have been corrupted by the Darkness, turning them more aggressive and violent, as well as being able to corrupt other humans into Rabids via blood contact.