Thanks for elaborating, MidnightShadow, I stand corrected. The witches can influence the environment of a mortal but their power doesn’t extend to death and damnation. That is a pathway Macbeth chooses for himself. The witches tempt and hassle Macbeth rather than altering his destiny.
“Though his bark cannot be lost, Yet it shall be tempest-tossed” tells of a ship’s master, whose wife rebuffed the first witch. The witches harry that sailor and, through a flaw in character, he dies by shipwreck nearing home (assuming the ship’s master and pilot are one).
Macbeth chooses to be king, rules with arrogance (a character flaw) and succumbs. As Hecate forecasts:
He shall spurn fate, scorn death, and bear
His hopes 'bove wisdom, grace, and fear:
And you all know, security
Is mortals' chiefest enemy.
In return, Macbeth and his wife are tempest-tossed by conscience, Banquo’s ghost, and the need to purge enemies - all credit to the witches. Nevertheless, Macbeth alone is responsible for his actions and for the havoc wreaked in Scotland. The witches aren’t to blame since “his bark cannot be lost”, though he himself can (and does) lose it.
Who is most "evil"? Lady Macduff and I reserve our votes for her husband.