What are the opposite words for reasonable?

The antonyms for the word "reasonable" include various adjectives that signify irrational, illogical, or emotional traits. For instance, "unreasonable" suggests a lack of fairness, sense, or soundness, while "illogical" indicates a lack of reasoning or rationality. "Emotional" implies a lack of logical or objective decision-making, as it originates from feelings and sentiments. Other contrasting words include "unjustifiable," "absurd," or "irrational," which depict an absence of reason or justification. In essence, the antonyms for "reasonable" connote an irrational, illogical, or overly emotional perspective, contrasting the adjective's sense of rationality and reasonableness.