Although Mesopotamians were familiar with the notion of sin, it is not sin that precipitates the Flood. The offence of human beings is simply that they multiply and, as a result, make too much noise for the gods' comfort. That such a slight and unwitting offence evokes such a lethal response is due to the shortcomings of the gods: they are tyrants - and stupid tyrants at that
How the floods came to be in the stories were different --one came to be because of sin and the other came to be because of too much noise. This surely paints such a negative picture of the gods in the Atrahasis Epic.