Wolverine and the Hulk have a deep history together, which includes multiple vicious fights between the mutant and the Jade Giant. In two separate What If storylines, the two killed each other - but which win was more brutal?
The What If series was created to explore key moments in the Marvel Universe if they unfolded differently. Issues include 'What If Spider-Man Joined The Fantastic Four?', 'What If Iron Man Had Been a Traitor?' and 'What If Gwen Stacy Had Lived?' The alternative looks at the universe proved popular. Disney+ is currently making an animated series based on the comic. One of What If's most violent series explored what would happen if Wolverine defeated the Hulk and vice versa.
'What If Wolverine Had Killed the Hulk?' (What If #31) takes readers back to The Incredible Hulk #181, the first appearance of Wolverine. While the two heroes still battle as they do in the original comic, Wolverine decides to kill his opponent by swiping his claws repeatedly at his neck. Shockingly, Hulk is killed after his throat is slit. The murder leads to a chain of events that has Wolverine joining the Brotherhood of Evil instead of the X-Men, and the issue ends with Logan killing Magneto after he attacked Jean Grey. As he is about to die, Magento uses the last of his power to unsheath Wolverine's claws and lunges them into his neck.
More than a decade later, the story of 'What If? The Hulk Had Killed Wolverine' (What If Vol.2 #50) was told. This time, Wolverine quickly dispatches of the Hulk during a mission in Dallas. After seemingly being defeated, Hulk rises and starts bashing Wolverine with all of his force. Hulk grabs Logan's head and snaps his adamantium neck - killing him instantly. Later in the story, Hulk killed Blob, Super Sabre, Pyro, and Avalanche in a deadly fight against the X-Men. In the end, Bruce Banner wakes up in a field and is taken into custody for murder.
In the end, both killings were surprisingly quick but brutal. Wolverine slit the Hulk's throat, while Hulk snapped Logan's adamantium spine. In terms of what is more brutal, it's a bit of a toss-up - but the Hulk snapping Wolverine's unbreakable neck is pretty nasty. Wolverine's victory seemed a little too easy, even if it let him down a villainous path. Hulk was nearly beaten before he killed his opponent. In this scenario, the Hulk's kill is more brutal. However, Wolverine killing the Hulk with his claws - even in a What If story is pretty remarkable.