User is able to induce mutations, changes in the sequence of an organism's genetic material, in self or other living beings. The changes can range from minor genetic changes to severe physical mutation, user could even be able to activate recessive abilities in allies or suppress abilities in foes. Note that the user may force instant change or stretch it over longer periods or even several separate sessions.
Mutagen (Teenage Mutant Ninja Turtles franchise) is a alien substance that serves as the key explaination for the mutation of the Ninja Turtles, Splinter, and most of the foes they fight. When the exposed to the mutagen, the affected person may experience a change in form, an increase in both size and strength, and may even experience a development in special powers.
When Osmosians (Ben 10) attempt to absorb too many life forms at once, their own DNA will be overwritten with alien DNA, causing them to become a chimeric mixture of those creatures.
A Xenocyte (Ben 10: Alien Force/Ultimate Alien) in the process of mutating a human host into a DNAlien.
Diva's (Blood+) singing can cause any human infected with the Delta 67 agent to mutate into a chiropteran.
When his body began to mutate as a result of its instability, Fusion Zamasu (Dragon Ball Super) called upon the Light of Justice...
...to spread said mutations to his right arm.
The mutant Infectia (Marvel Comics) utilized her ability for criminal self gain.
Orochimaru (Naruto) can force his subordinates and subjects into mutation via a Cursed Seal.
Mitochondria Eve (Parasite Eve) awakens the mitochondria in the cells of any life form she comes in contact with, turning them into horrific Neo-Mitochondrial Creatures.
Yume Hasegawa (Pupa) fed her brother Utsutsu some of her flesh to transform him into a monster just like her.
Christine "Four-Eyes" Yamata (Resident Evil: Operation Raccoon City) can use her knowledge of virology and a special gun to either infect humans with the T-virus or mutate zombies into Crimson Heads.
The energy from Dark Gaia (Sonic the Hedgehog) mutated Sonic the Hedgehog into a werehog.
Erazor Djinn (Sonic the Hedgehog) transformed into Alf-Layla-wa-Layla, what Sonic described as an "incomplete monster", when he absorbed 4 of the 7 World Rings.
Sh'Okanabo (Teenage Mutant Ninja Turtles; 2003 TV series)
The Corrupting Light (Steven Universe) was a weapon utilized by the Great Diamond Authority to corrupt and mutate the remaining Gems on Earth.
Diego Brando (JoJo's Bizarre Adventure) uses his stand, Scary Monsters to transform Gyro into a dinosaur.
SCP-40 (SCP Fondation) has the ability to manipulate living matter allwing her to modify existing life forms to create new ones. Her creations include a shape shifting sweater, a gasbag that plays tunes, and a fuzzy wuzzy wall crawling critter.