When the question in the title came up, all the answers seemed to be answering a different question, something like
What does it take to get a good job as a management consultant in a large consulting firm?
Lots of people who are not good consultants get jobs as management consultants in large consulting firms. And lots of good consultants can't get jobs with such firms. I know these things because I've been a consultant (a consultant's consultant) to a number of such firms.
If you really want to know what it takes to become a good management consultant, the answer begins with the observation that there are many different styles of good management consulting. The most important quality good management consulting requires is the ability to know yourself, both the good and the bad, along with the ability to retain the good things and improve the bad ones.
To take one example, consider health. I’ve watched many would-be management consultants fail because they couldn't control their drinking or eating habits when traveling on an expense account.
Or another example is would-be consultants who think their domain knowledge will be sufficient for doing a good job, but they lack "people skills." They believe, erroneously, that they can be arrogant, offensive, non-empathetic consultants but people will hire them because they're so smart and well-informed. They're wrong, and most of them never realize why they're failing. That's why I've written a number of books for consultants who wish to improve their consulting success:
Want to see a list of my books?