Though Dean was the obvious choice for the one to be barely unable to take watching Jo pummeled by a demon, John found himself approaching those levels as he lay hidden where even someone looking for him would be hard to find. Even Dean and Jo didn't know his spot, because he couldn't risk them glancing in that direction at any time. It had to be unexpected for even them. There hadn't been anything he liked about this plan, but using Jo as bait had been the part he liked least, because he would never forget another agreement just like that that had cost a Harvelle their life.
He hadn't been able to save Bill, it had gotten out of control, and the desire to make certain this didn't spin out of control was almost obsession-level right now. He wouldn't fail another Harvelle family member. He wouldn't fail another family member, period, and Jo and Ellen and Bill had been near family for years before Bill's death. He wouldn't see this yellow-eyed bastard harm another person, least of all his family.
Azazel. Didn't deserve a name, so it didn't matter to John he had one. He'd always been the yellow-eyed bastard and he always would be. The desire to look the creature in the eye right before he blew a hole in it was enormous, a gnawing, clawing ache in his gut that couldn't be ignored, but he knew he'd likely never get the chance. Shooting him unaware was the only option.
The wait between now and the moment to take action stretched on for a painfully long time and the clawing ache continued as Azazel advanced on Dean. Moving into position had to be a slow, careful thing, there was no room for error. It meant he needed that bastard focused entirely on them before the shot came.