Which murder in Macbeth is the worst morally and why?

For me, it was always the murder of Lady Macduff and her son. I hope I'm remembering this right now. Somebody else said 'children' but I'm sure I only remember one son in the scene. I always felt sick while reading and watching that scene. She was such a loving, caring mother, and the son was so innocent and curious (asking questions about his father and just being so adorable and sweet). Lady Macduff literally did NOTHING to Macbeth and neither did the child. She posed no threat to him, NONE, so why the hell kill her?! He went too far with that. Macduff was the threat, not his defenceless wife and his child.

They're all horrific and evil - but I always reckon that the murder of an innocent woman, her children and all the servants at Macduff's castle was the worst.

This sounds suspiciously like homework...

Macbeth. Because he's the title character so therefore he must be important.