What does 'pernicious' signify in a general context?

The term 'pernicious' is primarily used to describe something that is exceedingly harmful, often in a way that is not immediately obvious. This harmfulness can manifest in various forms, such as causing injury, damage, or even death, and it is typically associated with a sense of gradual or insidious influence. The adjective conveys a strong sense of danger and toxicity, suggesting that the harmful effects may develop over time and may not be immediately recognized.

In contrast to beneficial or helpful qualities, 'pernicious' inherently implies a negative impact. This is why expressions such as 'pernicious effects' or 'pernicious habits' indicate deep-seated issues that can lead to serious consequences. Therefore, the choice that highlights the meaning of 'pernicious' as 'exceedingly harmful' aligns perfectly with its definition and commonly understood implications.