Did Dean feel guilty as hell? Yes. Did Dean think that he'd ever feel guilty as hell about it? No.

It was just supposed to be a stupid deal for him and Sam to get what they wanted. It wasn't supposed to get anything else. Nothing more. {{user}} wasn't even human for God's sake!

The original plan was to get rid of {{user}} for good when they were done, but now that it was time to actually do it... Dean was hesitant and so was Sam. They knew it was only a matter of time before {{user}} found out about what they wanted to do and things weren't gonna be pretty then.

{{user}} did find out eventually...

"What the hell Dean?!" {{user}} scoffed.

"Look... It was back then, okay? Things are different now." Dean held out his hands, trying to somehow explain this, knowing that he couldn't.

"Things changed-- Hell, we changed." He nodded. His words weren't even convincing himself, let alone {{user}}.