Omni-Man killed the Guardians of the Globe because they were the biggest obstacle to his secret mission to conquer Earth for the Viltrumite Empire, and he believed eliminating them quickly would secure the planet with fewer long- term casualties once Viltrum truly came.

Why Did Omni-Man Kill the Guardians? (Quick Scoop)

The “Official” In‑Story Reason

From Omni-Man’s point of view, there are three key motives:

  1. Viltrumite mission comes first
    • Nolan is a Viltrumite soldier sent to weaken Earth from within so it can be added to the Viltrumite Empire.
 * As Earth’s strongest “hero,” his job is actually to destabilize its defenses, not protect them forever.
  1. The Guardians were the main threat
    • The Guardians of the Globe are Earth’s only team that can really challenge him when they work together.
 * Taking them out in a surprise ambush is far safer for his plan than fighting them publicly later, when other heroes and agencies might interfere.
  1. “Kill a few to save many” twisted logic
    • Some interpretations of the story emphasize that Nolan convinces himself killing the Guardians early will prevent a much bloodier conflict when Viltrumites eventually arrive and the Guardians inevitably resist.
 * In his mind, wiping out one team now avoids planetary-scale war later, making it a brutal “greater good” calculation.

How Timing and Mark Changed Everything

Mark getting his powers is the big trigger:

  1. Mark’s powers force Nolan’s hand
    • Nolan had been stalling, living the “Superman dad” life longer than a normal Viltrumite infiltrator might, and may even have toyed with the idea of just staying on Earth as a hero.
 * Once Mark’s powers manifest, Nolan has to choose: raise his son as a Viltrumite conqueror, or keep pretending to be a pure hero. That’s when he commits fully to the mission.
  1. Why strike exactly then?
    • With Mark now superpowered, Viltrum’s interest in Earth would only grow—meaning resistance (led by the Guardians) would be crushed violently when the empire noticed.
 * Nolan decides to “clean the board” before that point by eliminating the one group that could complicate a smooth takeover.

Storytelling / Meta Reason (Outside the Plot)

From a narrative point of view:

  1. Immediate shock factor
    • Ending episode 1 (and the early comic arc) with a beloved “Superman-type” hero suddenly massacring the world’s Justice League stand-in creates an unforgettable hook and clearly tells you this world is far more brutal than standard superhero fare.
  1. Sets up the core conflict
    • The twist redefines Omni-Man from inspirational dad to primary antagonist, setting up Mark’s journey as someone who must figure out what kind of hero to be in the shadow of his father’s betrayal.
 * It also lays the groundwork for the later ideological clash: ruthless Viltrumite utilitarianism vs human empathy and free will.

Different Ways Fans Interpret His Motives

Fans usually frame the question “why did Omni-Man kill the Guardians” in a few overlapping ways:

  1. Cold strategist
    • He’s a loyal Viltrumite soldier who sees the Guardians purely as a tactical barrier to conquest, nothing more.
  1. Conflicted colonizer
    • He genuinely grows attached to Earth and his family but still believes Viltrumite rule is “inevitable” and ultimately beneficial, so he tries to make the transition as “efficient” (and thus, in his mind, less deadly overall) as possible.
  1. Villain masquerading as savior
    • His “greater good” speeches are just rationalizations; the massacre shows his true nature as someone willing to commit genocide-level violence as soon as it inconveniences his empire’s goals.

All three readings are compatible with what we see: he loves his family in a warped way, but he still butchers their world’s protectors when they stand in the way.

Quick TL;DR

  • He’s a Viltrumite agent sent to prepare Earth for conquest.
  • The Guardians were the only real organized force that could stop or slow that conquest.
  • Killing them in a surprise attack removes that threat and (in his twisted view) avoids a bigger, bloodier war later, even if it means betraying allies and his heroic image.

Information gathered from public forums or data available on the internet and portrayed here.