Which term best describes something that is extremely evil or cruel?

The term "diabolic" is best suited to describe something that is extremely evil or cruel. This word originates from the Greek term "diabolos," which means "slanderer" or "accuser," and is commonly associated with the devil or malevolent forces. In modern usage, it conveys a sense of extreme wickedness, often evoking images of sinister intentions or actions that are particularly egregious in nature.

The other options do not align with the meaning of extreme evil or cruelty. "Malicious" refers to having the desire to cause harm, but it lacks the all-encompassing severity that "diabolic" conveys. "Forthright" describes someone who is direct and honest, and "beneficent" refers to acts of kindness and charity. Thus, while they may have negative or positive connotations, they do not capture the essence of profound evil or cruelty as effectively as "diabolic" does.