Allen the Alien was brutally beaten and left for death by Viltrumites on a previous issue. He then heals for a few months and his body became larger than before. He’s told that he’s now on par, even possibly stronger than Viltrumites.
I suppose in that sense he’s like the Saiyans, like Goku or Vegetan. When they’re near death, their powers increase.
From – Invincible #38