One point that I, being a 'Invincible' fan, can tell you is that there are an unusal number specific number for Viltrumites. This elusive species, once native to a score of stars and as numerous as the stars in their galaxy, suffered a devastating decrease in numbers because of its struggle for existence. Now the Viltrumites are a doomed race, distributed far and wide across the universe as a result of their bloody history.
Intriguingly, Viltrumites have an astonishingly long lifespan. They can live up to thousands of years. Their lifespan, teamed up with their superhuman abilities, makes them virtually unkillable under normal circumstances.
However, their age doesn't show as humans do. Their aging process slows down significantly after they reach their prime making them look eternally youthful. One good example is Omniman, looking in his prime despite being millennia old.
The strongest Viltrumite in the Invincible universe is Thragg, the former Grand Regent of the Viltrumite Empire. He’s not only physically the most powerful Viltrumite, but also the most battle-experienced, ruthless, and strategically brilliant.
Thragg was bred and trained from birth to lead the empire, making him a genetically perfect Viltrumite. His strength far exceeds that of Mark Grayson (Invincible), Omni-Man (Nolan), and even multiple Viltrumites combined. In fact, it took several top-tier characters working together—including Invincible, Battle Beast, and others—just to injure him, and even then, he kept fighting with terrifying endurance.
What makes Thragg especially dangerous is that his raw power is matched by intelligence. He understands warfare, manipulation, and long-term survival, which allowed him to rebuild the Viltrumite threat even after their empire collapsed. His final battles in the series are some of the most brutal and epic in the Invincible universe.