Which word conveys a sense of something being deadly or sinister?

The word that conveys a sense of something being deadly or sinister is "baleful." This term originates from the Middle English "bale" meaning "evil" or "harm." When something is described as baleful, it suggests an ominous threat, often implying a harmful intention or an aura of evil. It is commonly used to describe looks, actions, or presences that invoke fear or foreboding.

In contrast, "facile" refers to something that is easily achieved or effortless, which does not align with a sense of danger. "Redoubtable" describes something or someone that is formidable or awe-inspiring, often generating respect rather than fear. Lastly, "banal" signifies something that is unoriginal or lacking in freshness, thus devoid of any sinister connotations.