(Sam didn’t kill Azazel while he was possessing his father…) 

John Winchester: I’m surprised at you, Sammy. Why didn’t you kill it? I thought we saw eye to eye on this. Killing this demon comes first. Before me, before everything.

Sam Winchester: No, sir. Not before everything.

From Supernatural – Season 1 Episode 22: ‘Devil’s Trap’ (1×22) | Produced by The CW