On (怨, On; "Malice") is one of the defining features of the movie Hunter × Hunter: The Last Mission.[note 1] It is the opposite of Nen. Instead of utilizing life energy, the aura from On is derived from hatred and can be considered "death energy." On grants one immense strength, with each user being able to utilize abilities similar to Nen at 100% efficiency. Unlike Nen, this aura is said to be the stronger of the two and has no categories; meaning, one who masters On has the ability of an Enhancer, Transmuter, Conjurer, Emitter, Manipulator, and Specialist. It can be used after having contact with Jed's blood and making a contract to obtain On. However, the use of On will kill the user after the user breaks its contract (or, most likely, fails the contract). Jed, Gaki, Shura, Rengoku, and Gon are all On users in the movie.
- The kanji used for On (怨) can literally mean "grudge", "resentment", or "jealous".
- The kanji used for "On" is the same superimposed onto Gon and Killua the first time they felt Neferpitou's aura.