For me, the one that is more responsible for king Duncan's death is Macbeth because after all the things that happened he never thought about taking a step back and not doing it he decided to keep up with his ambition.
Macbeth has most of the blame because Lady Macbeth did not put the dagger on the king, Macbeth was the one that commits the crime that did all the work by himself if he wouldn’t want to do it then there was no reason for him he was already named Thane of Cawdor he went out that night and came back home with his hands and the dagger covered of blood “i have done the deed didst thou not hear a noise” we can’t blame his wife for something she did not put her hands on the king's body she just stayed home when Macbeth decided