How to beat the ugly monster

Can anyone tell me how to kill the big human/thing in POP Two Thrones.

Had the game since last year December and only got to play it now as so many other games to finish between my work and now i'm stuck on the level where i have to stick the dagger into his eyes but i keep failing.  Is there an easy quicker way or a trick to it.

Stealth kill thingy. Just climb on the wall (only at some points), jump on him and wait for the stealth kill screen thingy to appear before pressing the button.

Wrong forum, btw.