This was certainly the most intense episode of Breaking Bad ever.
I've been predicting for awhile that Walt and Jesse's relationship would hit rock bottom but then they would reconcile just one last time when Walt returned to town with the M60. This is how I see the finale going and the series wrapping itself up:
-Walt is nearing his death with the cancer and has also had about 7-8 months to reflect on everything he's done and he feels he owes it to Jesse to free him from the Nazis and get some sort of chance at redemption in Jesse's eyes. And it's a poetic ending to their relationship, as the whole series has basically been about them and their ups and downs. Their relationship right now is looking irreparable but that could simply be the significance of Walt coming back to "free" Jesse from everything once and for all.
-The Nazis, Jesse, Todd and Lydia are all there at the bunker or airbase or whatever to look over the current batch of blue crystal meth. Jesse is still a hostage, of course. Walt shows up and starts cleaning house with the M60. I don't know how many Aryans there would be but obviously, Walt isn't Rambo so I'm hoping his ambush on them is pretty believable. Maybe he targets certain groups of two or three at a few different locations before hitting the bunker. Either way, I doubt he'll need all four boxes of ammo and in the end, he wipes out Jack and all the others. During the shootout, Lydia is cowering in fear under a table or something and covering her eyes, and it's a wonderful callback to how she was acting in the second episode of these eight, with the way she was ducking and covering her ears while Jack and the Aryans wiped out Declan and his crew. The difference here is that it's the Aryans getting blown away with a machine gun.
-Speaking of which, I'm sure Jack's death will be similar to Declan and Hank's. It'll be him that is wounded and on the ground this time and then Walt will get the big moment of putting one last bullet in him (and probably spout off a few words to him beforehand.) Jesse in the meantime gets to kill Todd because Todd just has that one coming. Jesse hates Todd because of him mindlessly killing Drew Sharp and because he's made him his own personal meth cook slave for over half a year at this point. It's also a way for Jesse to get one last opportunity to say "Bitch", and he says it as he points a handgun towards Todd and shoots him in the head.
-Walt and Lydia then have a cup of coffee amongst the dead corpses. Sounds outrageous but that would be the dark comedy aspect of it. And Walt slips the ricin into her coffee and at the end of the convo, she says she has a flight to catch back to her hometown where she works for Madrigal. But of course, in a few days, she'll be dead from the ricin. Maybe we don't even see Walt slip her the ricin, maybe it's only revealed afterwards that he did it while he was making her coffee off-screen. Maybe Jesse asks him about why he'd let her go since she is a loose end but Walt tells him (as they watch her drive off in her car) that after a small dose of ricin, that problem will be solved shortly. I could see her death being this way because Vince Gilligan may consider himself to have too much class than to show Walt just gunning down a woman with a machine gun. Her death occurring off-screen like this would solve that.
-Walt and Jesse then talk one final time. Walt takes responsibility for most everything, apologizing for the poisoning of Brock and letting Jane die and saying Hank's death was ultimately his fault, and saying he understands why Jesse turned on him. This sounds a tad bit corny with me typing it but I can imagine it coming to life really well on-screen. Keep in mind there'll be eight months from now to the time this conversation takes place. Walt then allows Jesse to take the remains of his 11 million and if possible, most all of the money that Jack and his crew stole from him and disappear with it to start a new life. Walt then tells Jesse that it's only right if he is the one to put the bullet in him and finally put him down. Jesse might be reluctant to do so because Walt did just come back to save him and owned to all his past deeds and they do have serious history, but ultimately pulls the trigger. Either this, or Walt just outright kills himself. I think it's more fitting if he has Jesse do it, though.
-I really love the image of the aftermath of all of this when the police show up. Walt's corpse being surrounded by other corpses and his blue crystal meth lying all over the floor with blood scattered over it... it's a very poetic and symbolic sort of image. And the fact that Walt and Jesse's relationship ended for all time's sake here.
-In the aftermath, Jesse either reconciles with Audrey and Brock, or (most likely) just gives them a chunk of the money and leaves the bad memories of Albuquerque behind to start a new life elsewhere. Meanwhile, the police find all the corpses at the base and among them is Walter White. This huge massacre makes news, of course, and Skyler (if she is still alive since it looks like the Aryans might come after her next week and we know the White house ends up abandoned at some point) and Marie and maybe Saul Goodman (basically, all the major people formerly involved in Walt's life who are still alive) see the news and see that Walt has returned back to town and committed one last 'atrocious' act before dying. And this last act is the final chapter in the legacy of Heisenberg. The end.