I think DC kill bigger names in more graphic ways, whereas Marvel usually have their characters go out in a bit more of a "Blaze of Glory" however Marvel characters tend to get injured more. I can't count the number of times spidey has fought a villains whilst ill or with a broken arm or already beaten up, etc etc
One difference is with Marvel, they save their most hardcore stuff for their MAX comic line. While regular DC series like Infinite Crisis & 52 shows many bloody rampages, with crushed heads & flying limbs. What kind of ratings system does DC use?
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"I'm not smart so much as I am not dumb." - Harlan Ellison
As of Infinite Crisis, DC seems to be increasing the gore a lot, just paging through when the Green Lanterns and Yellow Lanterns were fighting, you see GL's getting head-shotted (seeing depictions of their brains literally flying from their head) and such, plus SBP ripping arms off and what-not.
Plus the recent Black Adam stories were over the top gruesome, such as where Black Adam cut open that snow creatures stomach and used it's intestines to repel down the side of the mountain.
You put that up against Civil War or World War Hulk, and for all the mayhem there is little graphic gore. Lots of bruised faces and torn clothing, but no spraying arteries.
But like I said earlier, Marvel instituted it's own rating system several years ago, and has distinct boundries with each level. DC's only restraint seems to be Superman never gets blood on his costume.
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"I'm not smart so much as I am not dumb." - Harlan Ellison