Lamech's disturbing boast shows how sin's impact on humanity has increased. Cain's descendants reached an extreme of violence with Lamech's contempt for human life. In his arrogance, he turned his actions into a poem.
avenged … seventy-sevenfold: God warned that anyone who tried to kill Cain would experience total justice (4:15). Lamech claimed that anyone who harmed him would face an even more severe penalty. This shows he felt accountable to no one, not even God.