Infinite Leveling System

It was difficult to describe the current situation on Earth. In the year 2100, after the great Quantum Age, two big news items destabilized the general situation of the whole world... The first big news was the existence of other intelligent races, creatures of the most diverse forms that seemed to be straight out of fantasy tales. The second big news was the existence of parallel universes, a news that almost drove the various world powers crazy with the possibility of expanding their domains beyond other dimensions.
However, these foolish dreams did not last long. Before mankind could take a step into the unknown, the unknown came to them. Suddenly, all of humanity was forced to deal with a joint attack by hundreds of foreign races, with each of their individuals carrying strange and extremely dominating powers.
500 years later, humanity had not been completely erased. However, the foolish ideas of supremacy that humans had carried for millennia had collapsed like a fragile house of cards. At this point, no human being would be foolish enough to try to regain the top of the food chain, not after descending hundreds of steps.