What would happen if Deadpool as Merc bent on killing every hero and villain in the Marvel Universe? The result: Deadpool Kills the Marvel Universe! Written by Cullen Bunn and with artwork by Dalibor Talajic, Deadpool will be going through four issues of chaos as he is going to kill every single character in the Marvel Universe. "Deadpool Kills The Marvel Universe" is a What if? story. Bunn said this:
I don't think there's any subterfuge in the title. This is Deadpool murdering the heroes and villains of the Marvel Universe we know and love. On another level, though, it's kind of a tragic story about being the puppet of greater forces -- and how far one might go to be free of all that.
If anyone remembers, Marvel did this same thing years ago (1995 to be exact) with the Punisher. Titled "Punisher Kills The Marvel Universe". It was written by Garth Ennis with artwork by Doug Braithwaite. It only had one issue and was also a What If? story.
So there you have it, and if you still don't have enough of what Bunn said above, check out these covers to the series (covers by Kaare Andrews).