Time travel, shape shifting, resurrection, etc. Powerful story elements that are almost always used wrong in comic books. If used right, they can make (rather than break) an awesome story. But more often than not, they are used as a crutch (deus ex machinus) to force a particular story down the throats of readers. “So, dey all were da Skrulls!!!” isn’t a very surprising or gut-wrenching twist.

Minor caveat – I didn’t read the Skulls stuff, but I have read other crap.