You can exclude words by using the minus sign. For instance, when searching for “pretty *” (i.e. “pretty” followed by any word) in COCA, “pretty much” is the first hit. If you’d like to exclude it, the search string “pretty -much” does the trick.
It’s even possible to exclude entire parts of speech, but only by using the old search syntax. If you change the search string to “pretty -[j*]”, adjectives such as “good” shouldn’t appear in the results anymore.