one-hit wonder; flash in the pan
Refers to a person or group that achieved a single major success but failed to repeat it, often used in entertainment.
彼は一発屋と言われているが、今でもあの曲は愛されている。
He's called a one-hit wonder, but that song is still loved today.
all-or-nothing gambler; one-shot speculator
Describes someone who stakes everything on a single risky venture, often in business or gambling.
あの投資家は一発屋で、一度の大勝負で財を成した。
That investor is a one-shot speculator who made his fortune on a single big gamble.
slugger; home-run batter
Baseball term for a batter who specializes in hitting home runs, often with a high-risk, high-reward style.
彼は典型的な一発屋で、三振も多いがホームランも多い。
He's a typical slugger; he strikes out a lot but also hits many home runs.
Compound of 一発 (one shot) and 屋 (person/shop), literally 'one-shot person'. The exact origin is uncertain, but it likely emerged in colloquial Japanese to describe someone known for a single big success.