Battle of the Abandoned Church

"If we do this, its a one-time deal. I'm in charge. You're the engine, but I'm behind the wheel. Understand?"

- Dean making a deal with Michael to become his vessel.

"I could... I probably should execute you. I could really, really use my imagination. But I'm feeling generous today. So one of you is gonna walk out that door and the other will be laying dead on the ground. You choose. (...) Or you could do that and I could murder you both and end all life in the universe. Remake it in my image, better than Dad ever could. I'm thinking... fire-breathing dragons. Sassy talking robots. I might give humans another chance if they know their place and worship me because I've earned it. But hey, it'll probably take a few days to unravel the universe. Maybe... seven, ten days tops. Maybe, just maybe one of you can stop me. Maybe. Well, let's see. Clock's ticking guys."

- Lucifer makes a deadly proposition to Sam and Jack

"Well, good try Dean. I'll give you that, buddy. But I'm not just powerful now. I am power. And I don't need a blade to end you, pal. Bye, bye, Dean."

- Lucifer's gloats to Dean moments before being killed.

"He... He's dead. (...) You did it!"

- Sam to Dean after Lucifer's death

"Thanks for the suit."

- Michael gains his true vessel

The Battle of the Abandoned Church is the final battle between the Winchester Family and the super-charged archangel Lucifer. The battle predominantly features Dean powered by Apocalypse World Michael who he is acting as the vessel to in order to defeat Lucifer once and for all.

Prelude
In an effort to rescue their mother and the Nephilim Jack from Apocalypse World, the Winchesters capture the archangel Lucifer, Jack's father, to continuously power the ritual to open a rift between the worlds. After learning from Rowena MacLeod that his son is in Apocalypse World, Lucifer breaks free of his magical bonds and is accidentally blasted through the rift by Rowena.

In an attempt to get to know his son, Lucifer resurrects Sam Winchester and makes a deal with him. Led to the Dayton outpost, Lucifer successfully bonds with Jack as the Winchesters prepare to evacuate a number of people from Apocalypse World through the rift for their own safety. During the exodus, Michael shows up and kills Gabriel in the fight that follows. When Lucifer tries to follow the humans through the rift, he is purposefully stranded in Apocalypse World by Sam where Lucifer makes a deal with Michael to share the ritual to reopen the rift in exchange for being allowed to take his son while Michael is allowed to destroy the Main Universe.

After arriving in the Main Universe, Lucifer kills a refugee named Maggie when she accidentally runs into him as he's scouting out the Men of Letters bunker. As Michael attacks the Winchesters and Castiel at a gas station and they barely escape, Lucifer finds Jack literally beating himself up over all of the people he has hurt and entices his son into leaving the Earth with him to find a new life out amongst the stars. Jack agrees, but has Lucifer resurrect Maggie first. After Lucifer and Jack leave, the resurrected Maggie tells Sam that she only saw her killer's glowing red eyes, causing Sam to realize Lucifer killed Maggie as Lucifer has glowing red eyes.

Before Lucifer and Jack can depart the Earth, Michael attacks the bunker and comes close to strangling Dean to death. Responding to a prayer by Sam, Jack returns to the bunker in time to save Dean and severely injures Michael. Before Jack can kill Michael, Lucifer appears and in the confrontation that follows, Lucifer's evil deeds are exposed, causing Jack to disown his father. Only really needing Jack's power, Lucifer steals Jack's grace, leaving Jack powerless and Lucifer super-charged. Lucifer teleports away with Sam grabbing on so he can go with them.

In the aftermath of Lucifer's disappearance, the weakened Michael tells Dean and Castiel that Lucifer won. Michael warns that after consuming Jack's grace, Lucifer is "juiced-up, super-charged" and will kill Jack and Sam and can potentially end the whole universe if he wishes. Though Michael had previously defeated Lucifer with ease it was while he was stronger and Lucifer was weaker. Michael tells Dean that while he'd love to tear Lucifer apart again, he is too weak, particularly in "this banged up meatsuit." As a result, Michael believes that they are facing the end of everything.

Remembering Zachariah and Gabriel telling him that he is the Michael Sword, Michael's one true vessel, Dean asks Michael if he could defeat Lucifer with Dean, the Michael Sword, as his vessel, which will make Michael stronger than he's ever been. Michael acknowledges that he knows what Dean is and that if they work together, they have a chance against Lucifer. Though Castiel protests, Dean believes he has no choice with Lucifer having Sam and Jack. Dean offers Michael a one-time deal if they do this: Dean will remain in control while Michael powers him against Lucifer. After Michael agrees, Dean consents and becomes Michael's vessel.

Battle
Arriving in an abandoned church, Lucifer berates Sam for grabbing on and coming with Lucifer and Jack. Letting go of a weakened Jack, Lucifer attacks the defiant Sam, beating and strangling him. As Lucifer begins killing Sam, Jack demands that Lucifer stop, causing him to drop Sam. However, Lucifer refuses to stop even though Jack is his son and beats Jack and Sam to the ground.

Lucifer taunts Sam by informing him that Jack has killed a lot of people, but Sam doesn't care as Jack is still family. Lucifer tells Sam about how family sucks and decides to prove it by forcing Sam and Jack to fight to the death. Drawing his archangel blade, Lucifer drops it between the two and tells them that he should probably execute them, but instead will allow the winner of the fight to live. Lucifer tells them that he plans to destroy the universe and remake it in his image and suggests that whoever wins, might be able to find a way to stop him. Picking up the archangel blade, Sam holds it out to Jack after a moment's hesitation and orders Jack to kill him. Sam tells Jack that if Jack survives, he can get his powers back and beat Lucifer. However, Jack doesn't think he's capable of defeating Lucifer but that Sam is. As a result, Jack begins to stab himself with the archangel blade so that Sam can survive, telling Sam that he loves Sam and everyone else.

Before Jack can drive the blade far into himself, Dean teleports in, now the vessel of Michael. Dean displays Michael's wings in a flash of light, causing Sam and Lucifer to realize that Dean let Michael in. Still in control of his body, Dean faces off with Lucifer, telling the fallen archangel that he and Michael had something in common: "we both wanna gut your ass."

As Lucifer charges him, Dean, powered by Michael, kicks Lucifer across the church, shattering a pew. Armed with Michael's archangel blade, Dean charges Lucifer and trades blows with him, but is quickly disarmed and thrown across the church. Getting up, Dean and Lucifer fly at each other and grappled in mid-air, trading blows before Lucifer kicks Dean backwards across the room. Remaining aloft, Dean flies back at Lucifer who stuns Dean with an uppercut and begins repeatedly punching Dean in the face as Sam notices Michael's archangel blade on the floor below Dean.

Beating Dean in mid-air, Lucifer gloats about his victory, not noticing Sam retrieving the archangel blade. Sam calls out to Dean and tosses him the archangel blade. Dean catches the blade moments before Lucifer begins smiting him. The smiting fails to kill Dean who stabs Lucifer in the heart with the archangel blade. In pain, Lucifer drops Dean to the ground before fire explodes from Lucifer's eyes, mouth and wound as the Winchesters and Jack watch. Finally, Lucifer's wings explode in a flash of fire and he drops to the floor, dead, surrounded by the burned impression of his wings.

Aftermath
In the aftermath of Lucifer's death, the Winchesters and Jack are left stunned that Lucifer is finally, truly dead. As they celebrate, Michael suddenly goes back on his deal with Dean and takes full control of Dean's body. With full control of his true vessel, Michael departs, loose upon the Main Universe.

Trivia

 * During the battle, Dean wields several of Michael's powers as he has said "yes" to Michael, but remains in control of his body while Michael powers Dean instead of having control.
 * Dean kills Lucifer with an archangel blade despite the fact that the lore states that only an archangel can kill another archangel with the blade. This is because of Dean acting as Michael's vessel with Michael powering him.
 * Team Free Will's original goal is accomplished with the death of Lucifer.
 * During the Apocalypse, Dean refused to become Michael's vessel because a fight between Michael and Lucifer would destroy half the world even if Michael won. In this case, it was a fight between Dean and Lucifer with Michael only lending his powers to the fight.
 * Dean becomes the Michael Sword to defeat Lucifer, a fate he fought against through Season 5. The Michael he becomes the vessel to is from an alternate reality rather than the Michael of the Main Universe.
 * While preparing to say "yes," Dean experiences flashbacks of Zachariah in Sympathy for the Devil and Gabriel in Changing Channels explaining his destiny as the true vessel of Michael.
 * This battle marks the first time a human has killed an archangel.