What religious group believed slavery to be an ultimate sin?

a. puritans.

b. spanish followers.

c. quakers.

d. oneida society?

Answer is: C. Quakers.

Quakers are members of a Christian group of religious movements.

Quakers played a major role in movement against slavery in the United Kingdom and in the United States of America. Quakers were some of the first whites to denounce slavery in the American colonies and Europe.