Both adverse and averse are used to indicate opposition. Adverse, usually applied to things, often means "harmful" or "unfavorable" and is used in instances like "adverse effects from the medication." Averse usually applies to people and means "having a feeling of distaste or dislike." It is often used with to or from to describe someone having an aversion to something specific, such as "he is averse to taking risks" or "he is risk averse."