I think that the Chief was accurate in reading the confrontation between Nurse Ratched and McMurphy as inevitable. To a great extent, the collision between Ratched and McMurphy's is the result of an unstoppable force meeting an immovable object. The Chief understands that their confrontation is inevitable. It cannot be stopped. The very essence of both characters prevents the other from being successful. In this light, the Chief is right in that the violent episode is inevitable.
The manner in which Chief describes both characters is where the inevitability of violent conflict between them exists. When the Chief describes McMurphy, he articulates a reality that underscores the freedom and zeal for life. This is seen when the Chief describes McMurphy's transformational effect:
I noticed vaguely that I was getting so's I could see some good in the life around me. McMurphy was teaching me. I was feeling better than I'd remembered feeling since I was a kid, when everything was good and land still singing kids' poetry to me.
This description highlights the joy of life and the irrepressible freedom that is intrinsic to McMurphy. There is an uncontrollable notion of freedom that is a part of McMurphy's being in the world.
Such a notion is diametrically opposed to Nurse Ratched's dominant and controlling vision of consciousness. In describing Nurse Ratched, the Chief understands clearly that her need to control and repress all expressions of freedom is the essence to her being:
So after the nurse gets her staff, efficiency locks the ward like a watchman's clock. Everything the guys think and say and do is all worked out months in advance, based on the little notes the nurse makes during the day. This is typed and fed into the machine I hear humming behind the steel door in the rear of the Nurses' Station.
In describing Nurse Ratched in terms like "watchman's clock, "efficiency," and a dehumanizing control of everything around her, the Chief understands that her will is not going to be denied. At the same time, the Chief understands that McMurphy's passion and zeal cannot be contained. McMurphy won't let it be controlled. In this confrontation, the Chief clearly understands that violent confrontation is the only possible option.