Which term signifies something that is deadly or destructive?

The term that signifies something that is deadly or destructive is "pernicious." This word is often used to describe effects or behaviors that, while sometimes subtle or unnoticed, can lead to significant harm or even fatal outcomes over time. The context in which "pernicious" is typically applied underscores its association with malevolence and danger, making it a fitting choice to describe something that is harmful or lethal.

In contrast, "benevolent" refers to a kind and well-meaning nature, which is the opposite of being harmful. "Beneficial" denotes something that is helpful or advantageous, further indicating a positive impact rather than a destructive one. "Innocuous" describes something that is harmless or not likely to produce any adverse effects, standing in sharp contrast to the idea of being deadly or destructive.