The kanji 酷 generally conveys the idea of severity, harshness, or cruelty. It can also refer to something being extreme or excessive. It suggests a strong or intense degree, often in a negative context.

・On-yomi (音読み): コク (koku) ・Kun-yomi (訓読み): むご（い） (mugo(i)) - cruel, heartless; ひど（い） (hido(i)) - terrible, severe

⚫︎残酷（ざんこく） Translation: Cruel; brutal ⚫︎酷暑（こくしょ） Translation: Extreme heat; scorching heat ⚫︎酷評（こくひょう） Translation: Harsh criticism; scathing review

The kanji 酷 is a 形声文字 (keisei moji), a phono-semantic compound character. The left side is a radical called 酉 (とり, tori), which originally represented a jar or vessel, later associated with alcohol. The right side is 告 (こく, koku), which means "to tell" or "to announce". Originally, this character had a similar meaning with 告(koku), but gradually, 酷 (koku) acquired the meaning of severity or harshness. The association might be from the idea of something being excessive or overwhelming, like a strong alcoholic drink.