Which Plasmodium species causes the most severe form of human malaria?

The Plasmodium species that causes the most severe and deadliest form of human malaria is Plasmodium falciparum.312

This species is particularly dangerous due to its high virulence, which is associated with its ability to infect a large proportion of red blood cells. Furthermore, red blood cells infected with P. falciparum tend to adhere to the walls of tiny blood vessels, or capillaries, leading to the obstruction of blood flow in vital organs. When this occurs in the brain, it results in a life-threatening complication known as cerebral malaria, which is frequently fatal if not diagnosed and treated promptly.3