According to wikipedia his character got worse in the last years of his life:
During his final years, and especially after the death of Hephaestion, Alexander began to exhibit signs of
megalomania and
paranoia.
[129] His extraordinary achievements, coupled with his own ineffable sense of destiny and the flattery of his companions, may have combined to produce this effect.
[178] His
delusions of grandeur are readily visible in his
will and in his desire to conquer the world,
[129] in as much as he is by various sources described as having
boundless ambition,
[179][180] an epithet, the meaning of which has descended into an historical cliché.
[181][182]
He appears to have believed himself a deity, or at least sought to deify himself.
[129]Olympias always insisted to him that he was the son of Zeus,
[183] a theory apparently confirmed to him by the oracle of Amun at
Siwa.
[184] He began to identify himself as the son of Zeus-Ammon.
[184