The adverb radically is a great way to say "in an extreme way." When your formerly long-haired friend shows up at work with a crew cut, you could say that she looks radically different.
Use radically to describe things that are done in a big way, particularly a change or an extreme position. For example, the government in your state might change radically after an important election. You'll often see the phrase "radically different" used to mean a change that's enormous, possibly even transforming. Though the root of radically, radical, originally meant "root of a word," it came to mean "far-reaching, innovative, or extreme," especially when it describes political views.