The success or failure of a movie can depend on so many things, but above all else it's whether or not a director and their cast are on the same page or not.
The annals of Hollywood are littered with legendary stories of the clashes between singular filmmakers and A-list talents, the results of which are either disastrous or miraculous. Usually disastrous, if we're honest.
And while many of the historical on-set feuds between directors and performers amount to nothing more than romanticised abuse, often directors will find brilliantly clever ways to manipulate the desired performances out of their cast.
At best these techniques can probably be considered cheeky and at worst pretty immoral, but each was at least a creative way to strongarm a visceral response from actors who, otherwise, would've struggled to create such a naturalistic response.
While they were certainly risky tactics, ultimately nobody was harmed by the deception long-term, and in each case the movie was unquestionably all the better for it...