Negative Corruption is spread through direct contact, not through some kind of virus or whatever. It can only corrupt beings with a soul, thus soulless beings are immune to it. If a corrupted grabs another being, corruption would spread through their body and try to teach their soul.
Becoming corrupted makes the being's entire body and soul turn dark red, and possesses its mind kinda in a way Clobers do. Their personality would twist into a smarter, "evil" one, hungry for multiverse domination. If the being was originally a minion, they would become the corruption source's minion, but if they used to have a mind of their own, they'd become the source's ally.
Corruption gives powers, the three main ones being higher intelligence, the ability to create corrupted portals through dimensions and double stats.
Monsters are instantly corrupted, because their souls are the weakest against corruption. Human souls can resist for a period of time that's decided depending on how powerful the soul is, but will eventually weaken and corrupt. The only type that can destroy corruption after a struggle is a Determination human soul.
The only two methods to cure a corrupted being is to rip the soul out, and erase the corruption through "Determination energy" or pure shortwave UV energy (if the being isn't weak against it, unless you want to kill them-) or to just completely destroy the soul lol