Remember, the X and Metroids are "natural" enemies. In Fusion, the SA-X was willing to die in order to destroy the Metroid lab and an X core willing to blow up BSL along itself. Later, a SA-X "saved" Samus from the Omega Metroid which in reality was just a self-preservation method.

The Chozo general informs Samus that she received two different strains of Chozo DNA as a child, one from the Thoha tribe, and another from himself, a member of the Mawkin tribe. The Thoha were responsible for creating the Metroids, designed to be the only predator of X, but also hostile toward the Mawkin.

The Metroid series is acknowledged as having borrowed many elements and plots from the Alien film franchise.

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.