Explanation:

- Evoking a keen sense of sadness or regret: This refers to something that deeply affects one's emotions, often causing feelings of longing or sorrow.

- Pungent: Typically used to describe a strong, sharp smell or taste. It doesn’t relate to emotions.

- Poignant: Often used to describe something that elicits strong, emotional responses, particularly sadness or regret. This fits the given group of words.

- Impactful: Means having a significant effect. While it can relate to emotions, it doesn't specifically evoke sadness or regret.

- Unaffecting: Describes something that doesn’t impact emotions. It’s the opposite of what’s needed here.