What is Macbeth's dying speech?
The last thing he actually says in the play is
Lay on, Macduff!
And curs'd be he that first cries 'Hold, enough!'
He's telling Macduff to get on with the fighting - and let the person be damned that asks for the fighting to stop first! Macbeth, at the last, goes out bravely, goes out fighting, and dies on the battlefield, just as he began.
But that isn't necessarily his dying speech. This is because Macbeth goes offstage, fighting with Macduff, and then, a little later, Macduff comes back with his head, which he has cut off. Macbeth dies offstage. So I suppose, in a pedant's world, you could make a good, reasoned argument that Macbeth could have said something else before he died. But Shakespeare doesn't record it.
Hope it helps!