There is only one intensive in English: the word “fuck” (or “fucking”). Listen to the actor declaiming:
O! What a rogue and peasant slave am I!
Note how he strains to make the derogatory language sound real, as if he really means it. Get him to put in a few “fuckings:”
O! What a fucking rogue and peasant fucking slave am I!
Hear how it immediately hardens and sharpens the images, makes them more like real anger and real self-disgust rather than disguised self-pity. Not just impressive but meant.
Should you keep these word substitutions in performance?
No.
...
There is another dimension to all this. All soliloquies, whether delivered to the (paying) audience or kept within the confines of the stage, are all really conversations beneath their surface.
There is the “you” voice —nagging, blaming, accusing, familiar from a thousand interior arguments:
YOU: You’ve got to get out of bed.
In opposition there is always the “I” voice —self-justifying, resentful:
I: I need just a few minutes more.
YOU: You always say that. You’re going to be late again.
I: That’s not fair. I’m never late.
YOU: Don’t make me laugh. And you haven’t even got a clean shirt...
... and so on.
To make this exchange clear, get the actor to split the two voices. Actually change the pronouns temporarily and then listen to the difference, especially with a few “fuckings” thrown in:
YOU: Yet I But you / a dull and muddy-mettled rascal, peak, / Like a fucking John-a-dreams, unpregnant of my your cause, / And can say nothing fuck-all...
I: Who calls me villain? Breaks my pate across...?
YOU: ’Swounds, I should you would fucking take it, for it cannot be / But I am you are pigeon-livered and lack gall / To make oppression bitter...
Hamlet Act II, Scene 2
If spoken with real conviction, the lines will emerge with a true note of rage and contempt turned inward against the speaker.