Ultimately, Breaking Bad is a study of the consequences of unchecked ego. It shows us that evil does not always enter the world screaming; sometimes, it slips in quietly, wearing the face of a desperate father, armed with a convincing justification. It teaches us that while matter can be neither created nor destroyed, a man’s humanity can be entirely consumed. Walt got what he wanted, but in the process, he evaporated the very man who wanted it. The equation is finally balanced, but the cost is paid in the lives he ruined. The chemistry is perfect; the tragedy is absolute.
While opinions may vary, here's a general consensus on the ranking of Breaking Bad seasons: breaking bad seasons
"No Más," "Caballo Sin Nombre," "Fly"