"man of commitment" is correct and usable in written English.
You could use it to describe someone who is dedicated to a cause, a job, or a relationship. For example, "John has been a loyal employee for over 10 years - he is truly a man of commitment."
The conventional way to describe Will, a type familiar enough from other movies (and, for that matter, from real life), is as a man afraid of commitment.
He was a man of uncompromising commitment, integrity and honor.
"You are also a man of heart, commitment, conviction.
Aaron was a man of passionate commitment to fairness and integrity.
He was a man of uncompromised commitment, integrity and honor who will be deeply missed but will continue on in our hearts, minds and love for each other.
One is that we accept the statements of Democratic and Republican senators that Mr. Ashcroft is regarded as a man of deep commitment and personal probity.
As the service opened, the dean of Westminster, the Very Rev Dr John Hall, said: "We come to celebrate the life and achievement of Richard Attenborough, a truly great man: certainly a star of stage and screen, but also a pioneer film-maker, an exemplary leader of his profession, a man of deep commitment, of great generosity of spirit, and of personal warmth.
A creative and uniquely talented man of strong commitment and outstanding intellect, Mr. Baker was elected Governor of The Society of the New York Hospital in 1977 and went on to serve on the Board of the merged NewYork-Presbyterian Hospithirdthe third generation of his family to do so.
My friends used to tell me teasingly that I was like a heat-seeking missile when it came to attracting men afraid of commitment.
Jacques Monod was a man of moral commitments.
