Im going to translate in this post, what the bleeding and bloody Sargeant has said:

Doubtful it stood;
As two spent swimmers, that do cling together
And choke their art. The merciless Macdonwald–
Worthy to be a rebel, for to that
The multiplying villanies of nature
Do swarm upon him–from the western isles
Of kerns and gallowglasses is supplied;
And fortune, on his damned quarrel smiling,
Show’d like a rebel’s whore: but all’s too weak:
For brave Macbeth–well he deserves that name–
Disdaining fortune, with his brandish’d steel,
Which smoked with bloody execution,
Like valour’s minion carved out his passage
Till he faced the slave;
Which ne’er shook hands, nor bade farewell to him,
Till he unseam’d him from the nave to the chaps,
And fix’d his head upon our battlements.

`1. At the first point the sergeant means a war between him and someone else, that for him means the art of kill or of the war

2. In the second one the merciless Macdonwald is proud to be a rebel and he is very strong, but he feels that he is been ignored and very weak inside him.

3. At the third one the brave king Macbeth said that all is weak for him and his glorious that is not being appreciated

4. The most important part of this is when he do the bloody execution that means that he was feeling brave and not being appreciated that he feels angry, and that’s why he do the bloody execution to his slave with his sword created with his passage or step.

5. This last part means when the king had killed to the slave without saying nothing to him and that was for demonstrate that anyone has to disrecpect him and that they have to be serious and put the head on, in the battlements.