Knowing that Thanos would solo Naruto verse, this would be unfair. But how about the most overpowered being in Naruto verse Juubi?
Thanos revives accidentally Juubi by using the power of The Infinity Gauntlet after uniting all the Bijuus only to see what happens, but he lost the IG for unknown reasons and have to fight the Ten-Tails with his normal powers.
As the original form of all nine tailed beasts, the Ten-Tails was said to possess massive and overwhelmingly foul chakra that is potent enough to bring total despair and destruction to the world. According to Kurama, not only is the Ten-Tails the source of all chakra, but is also the progenitor of everything that exists in this world. Kurama stated that it was a god that created countries and had the power to swallow oceans, split the land, and carry mountains. In addition, Kurama admitted that it alone wouldn't even stand a chance against the Ten-Tails, and stated that the Sage told them that its revival would result in the end of the world