Longevity
Sloth Wins
Sloth
The sloth lineage demonstrates extraordinary staying power, with ancestors appearing in the fossil record approximately sixty-four million years ago. Modern sloths represent the survivors of a family that once included ground-dwelling giants the size of elephants. Through ice ages, mass extinctions, and the arrival of apex predators including humans, the sloth has persisted by the simple expedient of being too slow and too unappetising to bother hunting. Their individual lifespan of twenty to thirty years in the wild compounds this evolutionary victory.
Thanos
As an Eternal-Deviant hybrid of Titan, Thanos possesses a lifespan measured in millennia rather than decades. However, his actual survival record proves somewhat less impressive than his potential might suggest. Despite his considerable powers, Thanos has been killed, resurrected, killed again, and ultimately erased from existence by Tony Stark. His philosophy of aggressive intervention, whilst briefly successful, ultimately resulted in his complete annihilation within a remarkably compressed temporal window.
VERDICT
Sixty-four million years of existence outweighs a few millennia ending in definitive death