Out of 100 consumers interviewed, the great majority of them loves (or love?) candies, and the 20% among them prefers (or prefer?) sugar-free candies.
As much as 30% of the consumers prefer (or prefers?) sugar-free candies.
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
When "majority" refers to a set of individuals, it should be construed as plural. The same goes for "20%" and "30%".
There is a usage note in that dictionary that gives this example:
"The majority of the voters live in the city.", (not "lives") since living in the city is something that each voter does individually.