Can it be me?

:^)

No. With great power comes with greater responsibility. Who knows if this leader misuses his/hers power, and the U.N. exists as a intergovernmental organization to promote peace, so a world with one leader is probably the leader of the U.N., but doesn't have full power and he acts as the officer.

The greek philosophers are attributed as identifying that a benevolent dictator is the best form of government, however human animals are tainted with the concept that ultimate power ultimately corrupts so we are damned if we do and damned if we don't. There is no solution to this question because it is an impossible ask.

For thousands of years civilisations have tried forms of rule from monarchy, feudalism and dictatorship, to democracy, nationalism and communism etc etc without ever achieving universal longevity. Whoever we are, wherever we are, we do the best we can in the hope that it is the best we can achieve, whatever that may be, and if we can try to live in tolerance of each others ideologies then so much the better.

One cooperative governmental organization, maybe.

One specific leader? Most definitely not.

Everyone has different views on what we should do with the world, so we need more than one leader so that we get more than one opinion listened to.