Which word best describes someone who expresses contempt or mocks others?

The word that best describes someone who expresses contempt or mocks others is "derisive." This term specifically refers to a tone or manner that is scornful or ridiculing, indicating a lack of respect for the subject being mocked. When someone is derisive, they are not just expressing a difference of opinion; they are belittling or making fun of someone else's beliefs, actions, or attributes.

In contrast, the other words do not convey this sense of contempt. "Compassionate" relates to showing kindness and concern for others, which is the opposite of mocking. "Affectionate" indicates fondness or warmth toward others, again lacking any element of derision. "Encouraging" suggests support and positivity, which would not involve contempt. Therefore, "derisive" stands out as the most appropriate choice for describing someone who mocks or expresses contempt.