The Flash's connection to the Speed Force gives him a speed advantage so vast that Omni-Man cannot compete.
Omni-Man is fast โ FTL by Viltrumite standards. But the Flash operates at a completely different level of speed. The Speed Force grants Barry Allen (or Wally West) the ability to move at speeds that make light look stationary, vibrate through solid matter, travel through time, and steal the kinetic energy from opponents.
Omni-Man's FTL combat speed is impressive, but the Flash routinely outruns beings who move at those speeds. The Speed Force is not just fast movement โ it is a fundamental force of the DC universe that grants abilities Omni-Man has no counter for. Phasing through Omni-Man's body, Infinite Mass Punch (striking with the force of a dwarf star), and speed stealing would each individually be fight-ending.
Omni-Man's durability is enormous, but the Infinite Mass Punch generates force that dwarfs planet-cracking. The Flash has hurt Superman with this technique. Against Omni-Man, it would be devastating.
The Flash moves at speeds that make Omni-Man look frozen. The Speed Force grants phasing, time travel, speed stealing, and the Infinite Mass Punch โ abilities that individually counter everything Omni-Man can do.
Omni-Man has FTL speed and planet-cracking durability. If the Flash makes a single mistake, Omni-Man's counter-attack would be lethal. His thousands of years of experience include fighting fast opponents.
The Flash wins through Speed Force abilities that transcend conventional speed. Omni-Man is genuinely fast, but the Flash operates on a different axis of speed entirely, with hax abilities that Viltrumite physiology cannot counter.
The Flash also fights
Omni-Man also fights