Which of the following words means fierce and cruel?

The word that means fierce and cruel is "truculent." This term is often used to describe someone who is aggressively defiant or hostile; it conveys a sense of being ready to fight or argue. When someone is truculent, they exhibit a fierce demeanor and an inclination towards brutal behavior, making it a fitting choice for the description provided.

In contrast, "indomitable" refers to someone or something that cannot be subdued or defeated, which does not specifically capture the aspect of cruelty. "Pungent" describes a strong, sharp smell or taste and is unrelated to behavior or temperament. "Virulent" refers to something that is extremely harmful or toxic, often used in the context of disease or poison, rather than describing a personality trait associated with fierceness or cruelty.