The particle くせに is used to express criticism, reproach, or dissatisfaction about someone whose behavior or situation contradicts what would normally be expected. It translates to "and yet," "even though," or "despite," but carries a distinctly negative, accusatory tone that sets it apart from similar conjunctions like のに.
くせに implies that the speaker finds the contradiction unreasonable or irritating. It often conveys blame, contempt, or frustration toward the subject.
While のに simply expresses surprise or mild disappointment at an unexpected outcome, くせに adds a layer of personal criticism or blame. Using くせに about someone can sound quite harsh.
Compare with the softer: お金がないのに、高いものを買った。(Even though he had no money, he bought something expensive.)
くせに is primarily used to talk about other people. Using it about yourself is possible but limited to self-deprecating or self-critical contexts.
Because of its critical tone, using くせに directly to someone's face can be very rude. It is used when complaining about someone to a third party.
くせに can appear mid-sentence connecting two clauses, or at the end of a sentence (as くせに) leaving the criticism implied.