The most radical type of change would be the Paradigm shift. Basing on the spectrum alone we can already tell that having the highest risk involve would likely mean it is the most radical type of change.

But what is a Paradigm shift? A Paradigm Shift is when a significant change happens - usually from one fundamental view to a different view. In most cases, some type of major discontinuity occurs as well. In laymen terms, Paradigm Shift is a popular, or perhaps, not so popular shift or transformation of the way we Humans perceive events, people, environment, and life altogether. (http://en.wikipedia.org/wiki/Paradigm_shift)

In an organization changing perspective means changing the way the organization manages and operates. How things work in an organization changes when a paradigm shift is applied. It sometimes lead the organization to a different direction. It will have a high reward if the organization shifts to the right direction and made some improvement. But if the organization shifts in a wrong way, they'll surely lose a lot.