Deadpool 2

Deadpool 2 (2018) — Wade forms X-Force, deals with a time-travelling soldier called Cable, and acquires a time-travel device he uses for petty personal revisions.

The TVA determines that the Fox universe (Earth-10005) is dying because its anchor being — Logan — died in Logan. The universe is scheduled for erasure. The villain is Cassandra Nova, Xavier's twin sister, exiled to the Void — the junkyard reality at the end of time where the TVA dumps pruned timelines. There they find survivors of discarded franchises: Elektra, Blade, Gambit, X-23, and the Human Torch from the 2000s Fantastic Four films.

How does Wade search the multiverse? He steals a TimeRipper from the TVA. It's their own multiversal transit technology, not something he invented.

And he already knew of Wolverine — in Deadpool 2 he mimics his poses and references Logan's ending directly. The joke is that Wade is a fan.

How is Wolverine alive if he died? He isn't the same one. The Logan of Logan stays dead — the film literally opens by digging up his grave and using his skeleton as a weapon. The Wolverine Wade recruits is a variant from another universe: one who arrived too late and let his own X-Men be slaughtered, and has been drinking about it since. Wade specifically goes looking for a Wolverine who's already broken.

How is the timeline saved? The TVA bureaucrat Paradox was using the TimeRipper to accelerate Earth-10005's destruction so he could get a promotion and build his own timeline. Wade and Logan destroy the device by grabbing its two opposing poles — matter and antimatter — absorbing enough voltage to kill anything, and surviving only because one regenerates and the other can't die.

But the actual save is quieter than the explosion. Hunter B-15 arrives afterwards to report that Earth-10005 has stopped decaying — the new Wolverine has taken over as its anchor being, replacing the one who died in Logan. Paradox had insisted an anchor being couldn't be replaced by a variant. He was wrong, and nobody at the TVA understands why it worked.