User blog comment:General MGD 109/Who's the strongest demon/@comment-4920092-20120510214500

1. Azazel. Before the WInchester's tore through the hierarchy of Hell, when everyone was still alive, he was in charge. Plus his incredible invulnerability to nearly everything (except being unable to cross iron). And he even said to John W. that "neither of them (Sam and Dean) are much of a threat," so at the very least, he believed that he would be immune to Sam's powers.

2. Lilith. The first demon, she took over after Azazel died. She's incredibly powerful, and likely immune to the knife (Ruby said it work, but she didn't want Lilith dead until all the seals were broken, so she was probably lying). It took an incredible amount of power for Sam to waste her.

3. Alastair. Able to travel between Hell and Earth with easy. Immune to the knife. Resisted Sam's first attempt to exorcise him. Able to easily overpower common Angels. Took an entire Enochian Circle to bind his powers.

4. Samhain. Uniquely powerful. Able to use energy waves similar to Lilith. Immune to Iron. Required specialized summoning.

5. Crowley. King of the Crossroads Demons. Able to be bound by a simple Devil's Trap (even after becoming the King of Hell), but displayed the unique ability to break the circle once inside it, using the knife.