- Yes - remember that it wasn't his idea in the first place as much as Lady Macbeth's ambition. At some stage surely he just loved his wife and followed her desires; there's evidence in places he didn't really want to kill Duncan.
- There was a sort of 'sliding' effect that ultimately led to his downfall. He was satisfied at one point to simply be king, but there's a lot to be said about his paranoid psyche that meant once one domino was knocked over (ie, killing Banquo) he wasn't really able to stop.
- Macbeth's life kinda sucked, if we're being honest. His wife gets power-mad, forces him to kill against his will, at multiple points shows signs of delusion, schizophrenia and (judging by the time period it was written and the superstitions about magic) the witches' influence, loses his best friend AND at the very end his wife - it's clear that despite his riches and power, even he knows it wasn't worth it.
- On that topic, look up Daemonology - it was a pretty influential book at the time, and influenced Shakespeare for Macbeth and Othello (which is an AMAZING link, if you have to compare to another book).
- At the beginning when he's told he'll be king of Scotland, he does show fear about how this would come to pass. Clearly he's a loyal man that, in the wrong circumstances, degrades into a broken man that loses everything. It's not as though he was evil and Machiavellian from the beginning.
- You could argue that Macbeth was spineless and weak-willed to not refuse killing anymore than Duncan. Granted there was probably an element of love involved, but even when Lady Macbeth starts regretting their deeds, Macbeth doesn't.
- The idea of sympathising with Macbeth as a broken man near the end (the "out, out brief candle" scene) is hard considering just how much evil crap he's done leading up to this - even if it was in mental illness.
- To be a "tragic hero", a character has to be one you can empathise to. Now, I don't know how many people you've killed into mentally-challenged stupor, but I think most people would probably not relate to Macbeth's prideful power-struggle.
There might be some things I'm missing - has been a couple years since I did English A2 ^^;