The Vorcha are a particularly psychotic and hostile species from the Mass Effect video game series. Typically acting as minions to the Blood Pack mercenary group, they are treated as cannon-fodder by their Krogan superiors. Vorcha on Omega are also employed by the Collectors to spread an anti-alien plague throughout the slums, which Commander Shepard helps put a stop to. Though frail and also incredibly stupid, the Vorcha have one major advantage in their regenrative abilities, which includes an immunity to all diseases, including the plague the Collectors contracted them to spread.
Though usually malevolent, it is worth mentioning that some non-evil Vorcha do exist, and some actively help in the war against the Reapers in Mass Effect 3.