A derogatory term for a foolish person, stronger than あほ. Often used in Kansai dialect but understood nationwide. Can be used as an insult or in a joking manner among close friends.
あほたれ！何してんねん！
You idiot! What are you doing?!
あいつはほんまにあほたれやな。
That guy is a real fool.
ばか is the standard Japanese word for 'fool', used nationwide. あほたれ is more dialectal and carries a rougher, more insulting tone.
Katakana spelling sometimes used for emphasis or in informal writing.
Kanji form using 阿呆; rarely used in modern writing.
Kanji form using 垂れ; very rare.
Derived from あほ (fool) + たれ (a pejorative suffix, from 垂れ meaning 'drip' or 'droop', implying worthlessness). The exact origin is uncertain, but it is a Kansai dialect expression.