Did Omni-Man beat Thragg?
As powerful as Omni-Man was he couldn't hold a candle to Thragg, who ultimately gave him the most brutal fight of his life.
Black Canary is one of DC's most gifted fighters, but it's her powerful sonic scream that could give her an edge in a fight with a powerful Viltrumite like Omni-Man. Her "canary cry" could destabilize him and potentially knock him out with a powerful enough burst.
He was trained in all manners of combat and bred to be the strongest Viltrumite. After their emperor, Argall was killed by Thaedus, Thragg fought in the Viltrumite civil war, meaning Thragg is thousands of years old. After the battle, The Viltrumites would emerge an unbeatable race led by him.
Battle Beast would win in any fight against a 'normal' Viltrumite including Omni-Man. The only exceptions would be Thragg or a mature Mark Grayson.
In the final moments of the fight, Thragg, having sustained far more damage than his opponent, breaks both of Mark's arms in a fit of rage and desperation. But Mark thinks quickly and then finally kills Thragg by ripping his throat out with his teeth.
Thragg Is the Strongest Viltrumite in Invincible
Without question, Grand Regent Thragg is inarguably the series' strongest Viltrumite.
Omni-Man's attempts to appease the Viltrum Empire ended in failure with his defeat and capture at the hands of his own people. He was held captive in prison until the Empire was able to send the required Viltrumite executioners.
The Immortal is a supporting character in Invincible. He is an immortal superhero and a member of the original Guardians of the Globe, now the sole surviving member after the others were brutally murdered by the former superhero Omni-Man.
Viltrumites can survive in space unaided. Sometimes confused with Interstellar Travel or Immortality, Self-Sustenance is a term used to describe the ability of some characters to survive and function without any form of nourishment, sustenance or energy such as air, food, water, sleep, etc.
If they're near a Yellow or Blue sun Kryptonians 17 or older will inherently have more strength than the majority of viltrumites (halfbreeds and younger). Also Kryptonian Society is equally war focused so they're combat skills would be on par.
How old can Viltrumites live?
Decelerated Aging: Viltrumites have the potential to live for thousands of years and still be in their physical prime.
After healing from his injuries, Beast was tasked to kill Thragg , who is currently in Thraxa. After days of fighting, Beast finally died when Thragg crushed his heart. Thragg will later use Battle Beast's skin as a cape and his body would be incinerated.

Space Racer. Perhaps one of the most mysterious figures on the list, the legendary warrior known as Space Racer was introduced in Kirkman and Ottley's Invincible #66, proved his worthiness against Omni-Man in battle nearly a hundred years before the series began.
The alien race established an empire that spanned the galaxy through their sheer brutality and force of strength, with their strongest capable of toppling buildings, flying at hypersonic speeds and proving completely invulnerable even to nuclear weapons.
Omni-Man has his own weaknesses with shedding his morals, and though he claims not to care for Mark and Debbie, the fact that he leaves instead of finishing Mark off proves that his son is likely his greatest weakness.
Thragg is the main antagonist of the Image Comics series Invincible. He serves as the most recurring villain and overarching archenemy of Invincible himself, as well as the most powerful villain he has ever fought.
Height: 6'10” Weight: 400 lbs.
So since Thragg, Omni-Man, and the Viltrumites are a deconstruction of Jor-El, Superman, and Krypton and so on; Superman always wins.
In addition to having all the generic powers and abilities of a Viltrumite, Omni-Man ranks among the most powerful Viltrumites to ever exist. He has superhuman strength, able to easily lift immense amounts of weight and tear through virtually any matter; this places him as the single most powerful being on Earth.
In the end, their battle waged for days, spanned the planet they fought on so rapidly no one else could interfere and left entire cities destroyed in its wake. In the end, Battle Beast thanked his opponent for the worthy death he craved for so long, and Thragg collapsed with his own life hanging on by a thread.
Who defeated the Viltrumites?
The Ragnar Aliens Can Kill Viltrumites
He coded all of the discoveries he made into science fiction novels he published on Earth, and one of the most daring tales he transcribed was his run-in with the Ragnars that proved powerful enough to maul a Viltrumite to death.