Which ruler was most responsible for uniting greece and building an empire?

Alexander the Great, was most responsible for uniting Greece and building an empire.

Explanation

Alexander the Great, who dreamed of conquering all lands in the world became the leader of Greek Kingdom on 336 BC.

Alexander ruled over Greece which he extended till India. This period is known as "Hellenistic period” spreading Greek culture throughout.

At a very young age, he created one of the largest empires of the world which still marks in history.

After his death, the Romans conquered his empire.

answer; ///he could not explain why the continents drifted;