Maybe it is because I've never gone to the DC board; but I can't recall any Marvel vs DC fan arguements. Scarlet Witch fans vs X-fans can get pretty epic (though it is more about defending than "rivalry"). OH!!!! Registration vs Cap's side was and still is a hot button issue. Film fans vs book fans? I've mostly not seen too many "rivalries" (but maybe I'm just blind).
This is the one that instantly popped in my head too. It's mostly died down (thankfully) though occasionally you do see some shade still being thrown.
The Scarlet Witch vs X-fans thing is pretty terrible
Crazed Sonic the Hedgehog comic book fans. They are terrible.
DC vs Marvel. Easily. There is always one troll in every thread that talks about how their company would never do THAT. And then a flame war ensues.
On the internet in general or just on this forum? If the former, well, DC vs Marvel, Sonic the Hedgehog, Bronies & Consolewars though admittedly since I've gotten older I barely see these anywhere outside Youtube comments and it's mainly the PC "master race", who manage to be far more annoying as they can't be excused away by being teenagers.
Many a 'shipping argument rapidly grow out of control. Especially if a segment of fandom fixates on a pairing that the writers had no intention of even hinting at.
Case In Point (one that proved considerably scarring): Zutara
Totally. There was a time where you could use a Storm/BP marriage thread like an hourglass. They used to be the place where some now permabanned posters would play the, "How racist of a thing can I say without being banned game?"
Inevitably, that is a game they would all lose. These days, much faster, thank goodness.
X-Books Forum Mutant Tracker/FAQ- Updated every Tuesday.
storm/bp marriage probably tops it. Though AvX stuff and x fans vs scarlet witch was/is pretty awful.
It probably doesn't count as a rivalry but many times when sexualization in superhero comics comes up, the debate turns bad.
I guess you guys forgot the following-
Sam Alexander vs Rich Rider-can't even get a review of Nova without Rich fans attacking it.
Ted Kord vs Jaime Reyes
HEAT vs Kyle (Green Lantern)
Black Panther vs folks who NEVER read his book even when Storm was there.
The Kord one is odd, because I see Jaime fans (full disclosure, started off a fan of Ted from Giffen back issues of JLI, but since he wrote Jaime's first stories he's basically a Giffen Blue Beetle so he's just as good in my book) talking about Ted fans not giving Jaime a chance or trying to keep Jaime down, and I see one or two Ted fans who tend never to talk about Jaime Reyes or much else aside form JLI appreciation threads. It seems to be a perceived slight, but certainly not the back and forth you get with the others.