Several parts combine into one character.

怒 is a phonetic-semantic compound: 奴 (slave / one who serves under coercion) provides the sound, while 心 (heart) provides the meaning. The composite metaphor is fierce: a heart driven and worked like a slave by some inner force — boiling, coerced, unable to settle. Anger in this view is not chosen but suffered, the heart pressed beyond endurance until it erupts. 怒 takes its place in the canonical Confucian list of human emotions: 喜怒哀樂 (joy, anger, sorrow, pleasure).

Korean reading is "no" (or "ro" by classical reading rules — Korean phonotactic rules convert initial r to n in modern speech). 憤怒 (bunno, fury), 激怒 (gyeokno, rage), 怒氣 (nogi, wrath), 喜怒哀樂 (huinoaerak, the four classical emotions — a phrase Koreans memorize from childhood literature lessons).

Mandarin nù, 4th tone. 愤怒 (fènnù, anger / fury), 恼怒 (nǎonù, irritated), 发怒 (fānù, to lose temper), 怒火 (nùhuǒ, "anger fire" = blazing rage). Chinese keeps 怒 in literary register; the colloquial verb is 生气 (shēngqì, "to grow vapor / steam" — also a wonderful image for anger).

Japanese on-reading ド (do) — 憤怒 (funnu / fundo, fury), 激怒 (gekido, rage). Kun-reading おこる (okoru, "to get angry") is the everyday verb — お母さんに怒られた (okāsan ni okorareta, "I got scolded by Mom") is something every Japanese child says. The literary kun-reading いかる (ikaru) carries gravity used in poetry. Critical homophone caution: 起こる (okoru, "to occur / happen") sounds identical but means something completely different — context decides which.

Memory aid: a heart (心) being driven like a slave (奴) — anger as the heart pushed beyond its limit.