"Cas couldn't have voluntarily allowed Lucifer to take over Jimmy's body," Dean said, disbelief latent in his tone of voice.

:

Sam sighed and made to walk away, laying a last comforting hand on this big brother's shoulder.

It was hard for Dean to take, Sam got it.
If there was one thing his brother hated it was to be let down by those he'd put his trust in, but in this case there was no mistake.

Back in the bunker, Sam had heard Castiel's words loud and clear.
The angel had accepted Lucifer in those last convoluted seconds before Rowena had completed the spell, allowing the archangel to be freed from the Cage and letting him loose on the world again.

The ultimate in a long series of dumb moves Castiel had made, for which both he and Dean had mostly forgiven him, though Sam wondered if they'd been TOO forgiving, acting like ostriches and hiding their heads in the sand, all for the sake of some tenuous friendship.

:

The truth was that Castiel had left a stream of murder, civil war and betrayal in his wake.
If they'd gotten rid of him in the past, many would be alive, including a myriad of Castiel's own fellow angels and comrades.

Not to mention what the angel had done to Sam himself.
Breaking his wall and bringing him to certain death through ever more delusional and agonising hallucinations hadn't been easy to forgive, especially when the century of torture he'd suffered at Lucifer's hands was still so fresh in his mind.

Of course, Sam had done it mostly for Dean.
His brother had somehow adopted the angel as his friend and in the name of that friendship was inclined to overlook his actions no matter how nefarious.
After all Sam mused in all honesty, he and Dean were no innocents either.

But this time Sam felt he wasn't ready to overlook Castiel's actions.
The angel had let Lucifer loose on the world on the off-chance that one archangel could succeed in killing Amara, when it had taken God himself and the team of four to confine her.

No, Sam mused. Castiel had become too much of a danger, consistently making the wrong decisions that put not only the Winchesters, but the entirety of humanity in peril.
As much as he tried to come up with an explanation for Castiel's action, Sam couldn't find a logical one.

:

Thanks to him, not only did they have Amara on their asses, compounded by her worrisome bond to his big brother, but Lucifer too.

And the only deterrent they might have had to keep Lucifer from killing him and Dean both, the need for Lucifer to have Sam as his perfect vessel, had dissipated now that Jimmy's body seemed to house the archangel perfectly.
They had nearly died back in the bunker, saved only by Lucifer's moment of distraction, giving Sam enough time to draw the angel-banishing sigil with his blood.

The younger Winchester felt his skin crawl as he remembered so naively asking Lucifer to use the energy of his soul to give him more power to bring back Dean from the past.
He felt violated, raped, the memories of what had been done to him in every shape and form back then, subjugated by the overwhelming power of Satan, returning in all their lurid details.

No, Sam decided weighing the pros and cons. This time he couldn't gather up any understanding for Castiel. He'd freely chosen to take in Lucifer. There had been no need, yet he'd done so.
Once again the angel had made a incompetent decision.

:

God knows he and Dean had made errors too but at least they had all been dictated by love, love for their brother, for the other half of their souls.

For whatever reason Castiel had done this, Sam was sure it hadn't been love that had fuelled it.
Knowing the angel, it was merely another badly thought out action that in his mind was going to save the world, but instead Sam reckoned sadly, had only contributed to dangerously upping the stakes.

Amara and Lucifer.
Who was to say they wouldn't iron out a pact? If Amara was impossible to put down, how would two mere humans like him and Dean manage against them both.

He gave a passing thought to Crowley.
Had Lucifer taken back his realm at last?
Not that Sam cared about the demon. It was mere curiosity on his part, though he calculated Crowley had either been killed or had become a grovelling minion at Lucifer's feet.
A further complication in the already dire spider's web of fuck-ups that surrounded them all.

:

Sam's heart was heavy, he knew his brother would take it badly, maybe even lay a few punches on him but Sam was more than convinced. Castiel had to be dealt with. The angel was too much of a loose cannon. He'd proven it over and over again.

If they ever managed to fix this Amara/Lucifer disaster, he'd kill him. Sam had put down beings for far less, and it seemed Castiel never learned from his mistakes.
He'd take this terrible burden on his own shoulders, for he couldn't ask Dean to eliminate someone whom he'd confided in and looked on as a friend, a friend who'd royally fucked up, but a friend nevertheless.

But Sam didn't see it that way any more.
Castiel had deliberately let Lucifer loose when it hadn't been in the least necessary, and in Sam's view it was the straw that broke the camel's back, at least for him.

If he got the opportunity, he'd run an angel blade though Jimmy Novak's body eliminating both Lucifer and Castiel.

He'd tried once before during the Leviathan fiasco to no avail, this time he'd not miss.

The end