I think Dean is a raw nerve right now. He's spent the last year neck deep in battle, to come back and find out that Sam took the year off has to grate. Regardless of any promises that they had made to each other, it's natural for Dean to feel abandoned by Sam. And he's just not in the right frame of mind to filter those feelings. Purgatory obviously hardened him. In order to survive, he was forced to embrace aspects of his personality that he's always tried to tamp down.

I, for one, am so happy to see such an twitchy, over-the-edge Dean. It's exactly what I was hoping for this season. We've seen Sam go 'dark side' but we've never really seen Dean do it.

I don't think that dean wasn't hurting when sam was gone !

I think the difference between the two is that Dean knew where Sam was and had no way to get him out. If Sam were to just disappear the way Dean did, Dean would've busted his ass to try to find him. Sam didn't even try.

^Also, Dean did try to get Sam out of Hell. It's not discussed in detail what he did but even though he'd promised Sam to let him go, he couldn't help but try to get him out.

I don't think Sam's choice to not look for Dean was out of character for him. It wouldn't be the first time he's retreated from hunting when things became overwhelming. He did it in the beginning of Season 5 as well. But unlike then, there was nothing/no one to pull him back in. He's never believed that it was the Winchester's sole responsibility to save people and at heart he's always wanted a normal life. Honestly, it's not one of my favourite aspects of his but I don't think we should judge him too harshly. He's been through a lot and he doesn't deal with things the same way as Dean.

^Wasn't it the other way around? Sam opened Hellgates and tried to make deals to save Dean after season 3, but I'm sure that Chuck's commentary at the end of Swan Song said that Dean stopped himself from trying to save Sam, much as he wanted to, because Sam had asked him to promise to leave him alone.

I'm a bit mixed over the whole Sam not hunting/Sam not looking for Dean thing. I'm pretty much bored of the brothers quitting hunting. I thought the whole purpose of the djinn targeting Ben and Lisa at the start of season 6 was to show that hunters can't ever quit without putting the normal people around them in danger. I get why Sam would want a normal life, he always has, and I get that the writers were trying to show this in order to have him willing to sacrifice it at the end of the series. But it still bugs me. So does Amelia.

About Sam not looking for Dean, it just seems out of character for me. And stupid. If they'd just included one line about him looking but having no idea what to look for/where to look, or assuming that Dean and Cas had both died.....