He really had no idea about Dean's time in hell, only that there had been some. But Azazel was good at figuring people out and he doubted the elder, more impuslive and in his eyes dimmer Winchester brother would have left without something he wouldn't be proud of. His reaction only solidified that theory.
Azazel didn't move to follow him just yet, grinning at Dean's almost over reaction. "You could have been, like me, given the time," he pointed out. "But enough talk, lets see if we can force someone's hand since it's clear blondie over there needs a bit more motivation," he flung Dean against the closest wall and started to walk towards him, stepping into the trap. With the realization that he had indeed been played even more than he had originally thought he lost his mental hold on Jo and she fell to the ground with a small groan though he still kept the one on Dean. Azazel looked down and then back at Dean. "Well... fuck," was all he said.