This is the 11224th most frequent Polish word.
grzechu
"Grzechu" means "sin" (genitive case) in English.
Here, 'grzechu' is used metaphorically to emphasize the value of an action or thing.
Wszystko, co robisz, jest warte grzechu.
Everything you do is worth a sin.
In this sentence, 'grzechu' refers to a state or emotion leading to moral wrongdoing.
Nie podejmuj decyzji w przypływie grzechu.
Do not make decisions in the heat of sin.
Here, 'grzechu' is used in its literal sense to describe a characteristic of a location or its history.