The SA-X is the main antagonist of the 2002 action-adventure game Metroid Fusion. It is the mutated armor of Samus Aran that was possessed by an X-Parasite, who searches for her throughout the Biologic Space Laboratories in an attempt to kill her.

Stick to the low ground and fire charged beam shots directly at the SA-X to destroy it. Your beam must be fully charged to damage it. As it approaches, Space Jump over the SA-X to the other side of the floor while charging your beam, and release the shot when you land.

The E.M.M.I. in Metroid Dread play a similar role to the SA-X. They constantly pursue Samus and are invincible to Samus's weaponry, though there are two notable differences: unlike the SA-X, they do not let up in their pursuit of her, and they can be killed before the end, though only with a certain weapon.

Samus nearly dies, but is saved by having Metroid DNA injected into her body, having lost her Power Suit as part of the process. This Metroid DNA ultimately makes her immune to infection, due to Metroids being predators of the parasite.