system
Given the following post, respond as if you're commenting on Reddit:
human
[Resident Evil] How does each virus turn things into monsters?
gpt
The T-Virus: Causes loss of higher brain function and inhibition, along with Horrific necrosis. At the same time, the structure of the infected tissues are changed and become vastly more durable, with the exception of the head where there is very little tissue covering the bone. Tyrants are individuals carefully infected in a controlled environment, and the result is more durable, stronger, and has enough remnant cognition to follow at least basic orders. 

The G-Virus: Does basically what the T-virus does, but without the necrosis, and is vastly more mutagenic. It causes Rapid cell division and mutation in an unstable pattern, leading to massive, cancer-like growths on basically every surface of the body, as well as major changes in overall body structure. William Birkin, our main example, was so mutated by the time he died that he no longer bore any resemblance to a human at all. Sherry Birkin, his Daughter, was only infected with the G-virus for a couple of hours, and she still retains an unholy rate of Cellular regeneration, allowing her to heal from seemingly fatal injuries in mere minutes.

Las Plagas: Are insect-like parasites that attach to and take over the brainstem (seemingly replacing the brain in its entirety at the end stage), allowing their hosts to either be commanded, or telepathically command other Plagas infected individuals. The parasites themselves are highly durable, and can survive even if the head they've infected is destroyed. This seems to be about as far as the Slave-strain of Las Plagas progresses. The command Strain, on the other hand, Appears to take over much more of the body, granting increased strength and durability while allowing the host to retain their personality and free will. Nemesis is a Tyrant infected with the Slave strain of Las Plagas, Granting it increased intelligence compared to a normal Tyrant, and making it much easier to control. 

Uroboros: Leech-like Parasites that form colonies inside their host bodies, bursting through the skin and surrounding their host like armor. It's mostly a strength in numbers thing. Very few mutagenic properties with this one, but the individual parasites are durable enough that bullets can't effectively reach the host body through the swarm.

The Mold (Name?): Essentially replaces the infected body in its entirety (e.g. Ethan Winters). The mold can, at that point, manipulate the shape of an infected individual as necessary for survival. Most infected appear to retain some semblance of free will, if not their original personality, and some rare ones can even exert a great deal of control over the fungus. Among these rare individuals, a good percentage of our known examples exhibit extra abilities, including remote control of their spores (In this case, contained in marionettes), and the manipulation of nearby magnetic fields (mechanism unknown). For some unknown reason, the mold petrifies when it dies.