What term refers to an opinion or argument that attacks another's viewpoint?

The term "polemical" specifically refers to a strong verbal or written attack on someone's opinions or beliefs. It embodies a confrontational tone and is often characterized by incisive criticism aimed at refuting or discrediting the opposing viewpoint. This term is commonly used in contexts where the individual is not just debating ideas but actively challenging and opposing another's perspective in a forceful manner.

In the context of the other options, while a debate engages multiple viewpoints and can involve criticism, it is more neutral as it encompasses a broader discussion rather than direct attacks. Refutation involves disproving an argument, which is a more structured and logical approach rather than an opinionated attack. A counterargument presents an opposing point of view to another argument without necessarily being aggressive or hostile. Thus, "polemical" stands out as the most fitting term for an opinion or argument that is explicitly attacking another's viewpoint.