noun which may take the genitive case particle 'no', na-adjective, noun
unfortunate; ill-fated; hapless
Describes a person or life marked by misfortune or lack of happiness. Somewhat literary and emotive; often used in set phrases like 薄幸の美人 (a beautiful but unfortunate woman).
彼女は薄幸の生涯を送った。
She led an unfortunate life.
薄幸な少女の物語に涙した。
I wept at the story of the hapless girl.
不幸 is the common, everyday word for 'unhappiness' or 'misfortune'. 薄幸 is more literary and emphasizes a poetic or pitiable lack of fortune.
Compound of 薄 (thin, light, slight) and 幸 (happiness, fortune), literally 'thin fortune'. The exact historical derivation is uncertain, but the meaning is transparent from the kanji.