I would say on the evil scale:
Tucco > Nazis > Salamanchas > Lydia > Todd > Crazy 8 > Walt = Gus > Mike > Jesse > everyone else
It's true, Walt is far more morally complex than just 'He's a bad guy'. People died who Walt did not intend to die through situations that Walt created through criminal actions. Walt is responsible for the murder of Drew Sharp even though he did not and would not have pulled the trigger. Making Jesse kill Gale was a survival necessity, poisoning Brock was a survival necessity. But if you put yourself in a situation where there is a chance you may have to kill somebody to survive, you are responsible for that killing and it does not count as self defense.
Walt did not intend most of the horrible things that happened as a result of his actions, but he is responsible because he did everything he did knowing it was a possible result.