A mecha design of a justice-seeking combat robot, heavy full-armor chassis with boxy angular frames and exposed cables, caterpillar tracks for legs, cylindrical head sensor glowing as it locks onto a target, wielding a beam-edged chainsaw weapon that sprays sparks as it slashes, equipped with an anti-missile catapult and thick shield, soaring over a swirling sandstone desert under a dramatic overcast sky, dust and oil stains visible on scarred armor, cinematic dynamic angle, intense amber sunset lighting casting long shadows, gritty realism and kinetic energy, volumetric sandstorm particles mixing with sparks and smoke.