Most powerful gay in world history

[Verily]

Roman Emperor Hadrian

Agreed, probably Hadrian. The Qianlong Emperor of China isn't a bad choice, either, but China was in serious decline relative to the rest of the world by that point (and you have to contend with conflicting stories about his relationship with Heshen as to whether he was actually homosexual).

[Verily]

Elagabalus

This one is really easy, folks.

My wiki does not suggest he was gay, per se, just decadent, and if one if equate power with long term influence, he was a nebbish.

Going by historical accounts, he appears to have been transgender, not gay. But there is a wide body of evidence that suggests the period historical accounts were attempts at slander by his successors, not what actually happened. Regardless, it is unlikely that Elagabalus was gay by any modern standard, while Hadrian most certainly was. And the Roman Empire was stronger in Hadrian's day than in Elagabalus's.

I think Hadrian was blatant enough to qualify as openly gay.

[Verily]

But if we look at lasting effects, Egalabalus was the founder of Christmas. Hadrian was the founder of a wall in Northern England.

El-Gabal existed as a target of worship, and his feast on the 25 December, long before Elagabalus tried to merge the sun cult and the state religion.

[Verily]

But if we look at lasting effects, Egalabalus was the founder of Christmas. Hadrian was the founder of a wall in Northern England.

El-Gabal existed as a target of worship, and his feast on the 25 December, long before Elagabalus tried to merge the sun cult and the state religion.

But Egalabalus is the main reason it is commemorated today, AFAIK.

Maybe. Constantine was officially a follower of Sol Invictus, too, and the cult was already common among the army (not as much as Mithraism, but close) by the time Elagabalus came to the throne.