expression, i-adjective
poor endgame; failing at the final stage; slacking off at the end
Idiomatic expression used when someone does well initially but makes careless mistakes or lets their guard down at the crucial final stage, leading to failure. Often used in business, sports, or games.
彼は仕事は速いけど、詰めが甘いから最後にミスが多い。
He works fast, but his endgame is weak, so he makes many mistakes at the end.
試合はリードしていたのに、詰めが甘くて逆転負けした。
We were leading in the match, but we slacked off at the end and lost by a comeback.
詰め is the noun meaning 'the final stage' or 'endgame', often used in compounds like 詰めが甘い or 詰めを誤る. It is not used alone in this sense.
甘い literally means 'sweet', but here it means 'naive', 'lenient', or 'insufficiently rigorous', implying a lack of thoroughness.
From the game of shogi (Japanese chess) or go, where 詰め refers to the endgame or checkmating sequence. 甘い here means 'lax' or 'insufficiently sharp', so the phrase literally means 'the endgame is lax', i.e., failing to finish decisively.