Macbeth was an honorable man through most of the play. He knew that the evil acts he committed were wrong, until the end of the book when he goes on a killing spree. When he kills Young Siward, Banquo, and the Macduffs he is pure evil. He turned into a cruel tyrant from being paranoid of others taking his throne. He rose to power by being evil, and tried to stay in power by being an evil, and cruel tyrant. When he'd kill people he'd mock there dead bodies, and that is very evil to be trash talking to someone that you've just killed.
Macbeth never would've committed any evil acts had it not been for Lady Macbeth. He had thought of killing King Duncan because of the witches prophecies, but said "Vaulting ambition, which o'er leaps itself And falls on th' other" (1.3.27) This quote is saying that Macbeth doesn't want to murder a good king because of his own ambition. Lady Macbeth makes Macbeth think about killing Duncan, and makes him do it so she can have more power. She tells Macbeth to "Look like the innocent flower, But be the serpent under it." (1.6.65) What she's saying here is that Macbeth should pretend to be innocent, and benefit from the evil you've committed.
Overall, Macbeth is a statement of evil due to all his evil deeds he commits and his easily tricked mind. This play is based around evil, with the witches starting to have Macbeth think evil thoughts, then Lady Macbeth making Macbeth commit evil crimes, and then Macbeth being consumed by evil. Macbeth per se was not evil at all, but was lead to be evil by others. In the play characters say that Macbeth is the evil person, when there are others that go under the radar, and are the real cause of evil. The witches placed a thought in Macbeth's that eventually led to him killing many people, and become evil.