How do you kill the sax boss on metroid fusion?

Answer 1

The SA-X is only vulnerable to a fully charged blast from the plasma beam. When it first appears, land one hit on it when it is on the platform, then drop down to the floor. From there, what you want to do is get the SA-X behind you, then turn around and fire your shot. Jump as soon as you can and screw attack over the boss to Dodge its scre attack. Repeat this until it moves to the second phase. A good way to evade the second phase it to jump up to the highest level of the room, where it can't reach you. When it jumps, jump up and shoot straight down. When it goes to the core-x phase, drop to the floor, charge up or missiles and shoot at its eye, then screw attack over or through it. Jump immediately to avoid its shot. Repeat this until it is finished. A skilled enough player can use this to finish the fight without taking a single hit. See the video below for an example.