How and why does Macbeth go from war hero into evil murderer?please help me with this queston (thanks alot):)

We see the transitional period of hero-villain from Macbeth as I believe the witches prophecy were a catalyst to have that vaulting ambition to become thane of Cawdor. However as  this was his Achilles heel, Shakespeare represents Macbeth as a tragic hero as his wife lady Macbeth is very eager for the killing of Duncan to emerge quickly, the use of reverse psychology encourages his ‘vaulting ambition’ which drives him on to become a degenerated Macbeth. Add quotes

Shakespeare characterizes Macbeth as a man who has fatal flaw in his egotistical mind. ’the greatest is behind’ we see he clearly commits acts of hamartia, however knowingly he senses he is in  danger of his throne killing innocent friends such as banque Macbeth  degenerates  slowly becoming a power hungry animal. Lady Macbeth exploits his weakness to kill and making Macbeth a tragic hero. The Witches spark the ambitious nature in Macbeth and whisper ‘like the devils to his ear’ the words that open his greed.

As the say ‘power begets power’ we see clearly the moral decline of Macbeth in act 1 because the prophecy reassures his authority of becoming thane. However we see his guilty conscience coming into play, thus affecting his mind, unsure whether to kill Duncan or not or face the consequences (quote).