so stupidUsed to criticize someone or something as unintelligent. The adjective changes form to agree with the noun: такая тупая for feminine nouns and такие тупые for plural nouns. It can sound insulting, especially when referring to a person.
RU: Он такой тупой, что даже не понял шутку.
EN: He's so stupid that he didn't even understand the joke.