Mastered Ultra Instinct Goku opens at his absolute ceiling, and it shows. His body moves without thought — every Saitama strike arrives and Goku is already gone, reading the trajectory before the fist finishes forming. He feeds that precognition into a relentless offensive, stacking God-ki Kamehamehas with teleporting repositions, forcing Saitama to swat energy columns the size of continents while Goku materialises behind him again, again, again. Saitama eats every detonation without flinching, his abnormal pain tolerance absorbing what would incinerate lesser beings, but Goku keeps the pattern perfect — never overcommitting, never standing still long enough to be caught. For a stretch that would qualify as the greatest fight in Goku's career, Ultra Instinct makes him functionally untouchable.
Then the toll arrives. Divine Avatar form burns through energy at a rate nothing in mortal biology was designed to sustain, and Goku has been running it at maximum output the whole time. His reaction windows shrink by fractions — imperceptible to anyone except an opponent whose enhanced senses are precisely calibrated for this. Saitama clocks it. No announcement, no posturing. He stops chasing the teleports and starts positioning where Goku will be, letting the Ultra Instinct automation run itself into his fist instead of away from it. A Serious Punch connects flush — not because Goku slows down, but because the margin that made him untouchable has thinned to nothing.
Goku catches himself mid-air, breathing in ragged pulls, divine aura guttering. He grins through the blood. "Not bad." He summons what's left for one final God-ki surge — and Saitama is already there, another Serious Punch already moving. This one doesn't let Goku finish the sentence. The shockwave peels across the empty planet in silence.
WINNER: Saitama REASON: Goku's stamina drained under the sustained cost of Mastered Ultra Instinct, narrowing his precognition margin until Saitama's enhanced senses and Serious strikes could finally land decisively.