flaw

(noun) an imperfection in an object or machine. Synonyms: defect, fault. Examples: "A flaw caused the crystal to shatter." "If there are any defects you should send it back to the manufacturer."

(noun) defect or weakness in a person's character. Example: "He had his flaws, but he was great nonetheless."

(noun) an imperfection in a plan or theory or legal document that causes it to fail or that reduces its effectiveness.

(verb) add a flaw or blemish to; make imperfect or defective. Synonyms: blemish.