How to say "unethical" in Japanese

• 乱倫らんりん
  no-adjectiveReally a word for sexual immorality — corrupt, sexually improper conduct — and a less common one; it is seldom what you want for 'unethical' in the sense of unethical business, research, or everyday conduct.
• 非道徳的ひどうとくてき
  na-adjectiveThe direct equivalent: it describes actions, practices, or decisions that violate accepted moral standards — the natural choice when you need 'unethical' for conduct judged wrong on ethical grounds.
• 背徳的はいとくてき
  na-adjectiveCovers 'unethical' with a stronger coloring of moral corruption or transgression, a suggestion of the illicit; it suits something tainted by moral decadence more than a neutral verdict that conduct violates ethical standards.

For plain 'unethical' conduct choose 非道徳的; 背徳的 adds a nuance of moral corruption or illicitness; 乱倫 really denotes sexual immorality and is seldom right for ordinary unethical behavior.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 乱倫らんりん(sexually) immoral
• 非道徳的ひどうとくてきimmoral
• 背徳的はいとくてきimmoral
• ブラックexploitative (company)