Which term would best describe an action that leads to harmful consequences?

The term "pernicious" is used to describe actions or effects that are harmful, often in a way that is insidious or not immediately obvious. This word carries a connotation of something that causes damage or injury, especially in a gradual or subtle manner. In various contexts, actions deemed pernicious may not only have direct harmful effects but can also lead to longer-term negative outcomes. Given its strong implication of harmfulness, "pernicious" is the most appropriate word to describe actions that lead to harmful consequences.

In contrast, "benevolent" refers to actions that are kind and well-meaning, while "innocuous" and "harmless" denote a lack of harmfulness or risk, further reinforcing why they do not fit the description of leading to harmful consequences.