Does Macbeth determine what happens to him?
Macbeth is certainly the one who determines the course his life takes. The moment he decides to murder king Duncan is the moment he accepts evil. Once he does that, he cannot go back to the point when he was considered to be a loyal and good warrior, ready to support his king and others.
Macbeth's ambition consumes him, and although he is motivated by the witches' prophecy and pressured by his manipulative wife, he does have free will to decide who he wants to become. He decides that he wants to pursue his ambition even though it entails resorting to the most unlawful means.
Once he gets rid of king Duncan, he cannot stop. He begins to murder many other innocent characters, such as Banquo and Macduff's family, because of his obsessive desire for security. He does not want to allow his power to slip away from him by letting others stop him from being the leader of the country:
I am in blood
Stepp'd in so far that, should I wade no more,
Returning were as tedious as go o'er:
He states that going back to the point when his conscience was clear would be as tedious as going forward. He believes he should continue being ruthless and evil because he cannot erase the crimes that have already accumulated.
Macbeth's desire to get rid of anyone who stands in his way eventually leads him to his imminent downfall. So, he is the one to blame for his death.