Another arc I really liked was the so-called Cancerverse storyline Marvel ran a few years ago. Basically in the main Marvel U, Captain Marvel succumbed to cancer and died. In this alternate timeline, the heroes decide to save Captain Marvel by any means necessary. Eventually this means killing the personification of Death in the Marvel U, which inadvertently lets the Lovecraftian Old Gods into the world. The heroes gets possessed, chaos ensues, it's all a good time. You can check it out in the Realm of Kings arc (must read the one-shot first, it sets the whole thing up) and the story concludes in the Thanos Imperative storyline.
The Defenders in the Cancerverse.
And the Avengers, known as the Revengers.
Sorry the images are so large.