Omega-level
Senior Member
1- Ressurections: Damn Jean Grey... If i'm wrong, she was the first character, at Marvel at least, to return from the dead which was originally intended to die. If not the first, she was certainly the one which made it fair game. Now, a character dies and you start to count the minutes from it's return.
2- Alternate reality characters: Don't get me wrong, i'm OK with alternate realities, but the characters from these realities should remain there and the 616 ones at best pay a visit and go away.
3- Retcons: Every story you love has the risk of sooner or later be ruined by a writer who will create some background story which changes everything, and sometimes ruin these stories or some characters forever (hello, forget everything you read or know about her, Gwen Stacy is a WHORE!).
4- Everybody knows everybody: Sooner or later, you'll find out that your favorite character, the one which you know everything about, has a past with another character you know, even though there's no mention of it or any indication at all in the 500 times they encountered before. Wolverine specially knows the entire Marvel Universe, he probably even went to a strip-club with Thanos and Black Bolt in the 60's... and they fought Sabretooth in the ladies bathroom.
5- Inmate breeding: Of course, it helps that every chick which is not a Morlock is hot and most male heroes are good looking or at least strong and manly, but why do every character on a group must be attracted or in love to at least one other member of this group? This happens in nearly every group, except for the Fantastic Four, but in the X-men specially. Why they can't just go out, damn it? They're all powerful, and have at least money enough to buy some flowers or to pay for a motel room, go find a chick/dude elsewhere!
In all cases, there are exceptions, of course, but generally few.