CONTAINS SPOILERS

Nemesis' weakpoint is the red glowing area center of its chest. Run and strafe left and right when the blue/orange bullets fly at you. Dash at the last moment when the purple homing missiles fire. Once his minions glow yellow, they fire lasers. Dash through them. When falling, scan around and grapple to the platforms closest to him. Stay on the edges so you can dodge attacks and shoot its chest.