Source: marvel.com

4. Wolverine

(X-Men/Wolverine, Marvel Comics)

The seeds for Death of Wolverine were sown very early on in the preceding Wolverine run, in which a microverse virus infected Logan and shut down his healing factor.

When the clawed canuck discovered that a bounty was placed on his head, he set off to find out why. After a couple of dead ends, Logan eventually found Dr. Abraham Cornelius, the mastermind behind the Weapon X Project. Cornelius wanted to steal his healing factor in order to perfect his attempts at re-creating a more controllable version of Wolverine.

Wolvie revealed that he’d lost his healing factor, and Cornelius went nutter-butters. He started initiating the adamantium bonding process on three innocents, knowing that it would kill them. Unfortunately, this resulted in Logan being covered in slowly hardening adamantium. He stumbled to the roof, watched the sun rise, and suffocated to death in metal.

Since then, we've had Old Man Logan bouncing around, and X-23 has put on the Wolverine costume, but we've been missing classic Wolvie.