How Did He Die?
Wolverine has of course died a bunch of times, but his healing factor always comes through in the end - one time even from a molecule remaining on his barren skeleton. There have only been two times where he was thought to be properly, clinically dead for a long period of time. The first being when Apocalypse had a mysterious new incarnation of the Horseman Death by his side in the run-up to 'The Twelve' storyline. Wolverine tried to go toe-to-toe with him and was run through with a big scimitar, killing him.
How Did He Come Back?
The Wolverine that died was revealed to be a Skrull imposter, sent to gather information on Earth's heroes, whilst the mysterious new Horseman was actually revealed to be a real, brainwashed Wolverine. The ol' switcheroo!
Wolverine recently died again, in 2014's Death of Wolverine limited series; he was calcified in adamantium after killing Professor Cornelius, the man responsible for his metal skeleton, and freeing a bunch of Weapon X experiments.
Thought dead until recently, the character has now mounted his return in Marvel Legacy, curtesy of some cosmic interference. Logan has an Infinity Stone, and while he's never been a cosmic character in the traditional sense, he looks to be playing a pivotal role in the Marvel Universe going forward - Old Man, or not.
Have we missed out any X-Men to die and come back to life? Let us know in the comments below!