Well, let's start with the death list and injury roster!
I think I counted Smoke Monster/Locke shooting to death 17 or 18 people, he snapped the neck of at least one other, and in his smoke form killed at least a couple more (Sayid conveniently knew how to disable Widmore's EM fence).
Crazy Claire killed at least a couple of the expendable Widmore people (but, alas, Billie Jean King clone still lives for another ep at least) ... no sign of Widmore. No Desmond this ep. What happened to Miles?
Next ep, Across the Sea, is the flashback to how it all began - the backstories of Smoke Monster/Man In Black and Jacob. So that only leaves the eps What They Died For and a 2-parter, The End to explain it all.
After this ep, I'm kinda feeling shorted. Too many of the principals crowded together but not doing much. They go to the plane planning to fly it away (er, with what runway and with blown sand in the engines and no gas?) - but Smoke Monster/Locke finds a bunch of C-4 Widmore had hidden away on the plane to blow them all up (specifically Smoke Monster/MIB/Locke because that's who Widmore is after). Locke then leads them to the sub - they'll leave that way. Jack says he'll stay behind but Kate gets shot and so he helps get her on the sub (after pushing Smoke Monster/Locke in the water they way kids at camp do) and then climbs aboard himself. Sawyer is playing boss and says to leave Claire, who stupidly doesn't seem to notice that they're leaving without her.
But wait, there's a twist! Our main characters escape in the sub, but meanie Smoke Monster/Locke put the C-4 in Jack's backpack and it has a timer, but Jack realizes they must not do anything because the island won't let them die, they can only kill each other or themselves if they try to disarm the bomb - Sawyer can't process that in his Cro-Mag brain and finishes his fit of machismo and a quicker timer now races to ZERO and Sayid suddenly grabs the explosive device and runs with it and saves most of the rest of them and gets ... blown to bits. A sub door flies loose and kills Jeff Fahey's pilot character (they kept him around all this time to kill him like this?), and Sun gets trapped and Jin decides to stay with her and they lovingly drown together. Sayid tells Jack about Desmond and then tells Jack "It's going to be you" i.e., our candidate. Weirdly, Sayid tosses that off almost as a throwaway line, mumbling almost and looking down and almost out-of-frame (writers', director's choice?).
Only Sawyer (who saves Jack), Hurley, and Kate make it to the beach. Hurley breaks down and sobs and they shorted Jorge Garcia a real moment - he could have conveyed Hurley's deep sadness and the futility of it all if they've let his emotional reaction play out longer.
In the Alt+B timeline lots of Jack (and everyone intersecting again - Jin in the hospital hallway with flowers for Sun ... Leela - er, I mean Katie Sagal, pops up re; father stuff). Dunno what's up with the creepy dentist who seems to know stuff and intones mysteriously to Jack. The father complex stuff is played out and Jack tries to reach out to Locke who again refuses him. A music box is left to Claire and she and Jack open it but don't really listen to it's tune nor look through it more thoroughly ... oh, and bad acting alert: Emilie de Ravin (who plays Claire) didn't even attempt to move as though pregnant - that fake baby strapped to her real tummy didn't seem to weigh anything when she moved.
This episode felt very much like that Dave Chappelle skit Wrap-It-Up