Violence is a sore subject with comickers. Too many of us are gamers or love the occasional horror movie, and violence is a part of that entertainment. However, you have those that think that exposure to any form of violence will cause the person to be violent as well. Because of this writers make a conscious decision to be either non-violent or ultra-violent. That needs to stop.
When you decide on how violent your comic world will be, you need to be make without worrying what other people says. I'm obviously ignoring satire and parody here, where the consideration of others is pretty much the point, but you need to make the decision on what level you want it to be, where it feels good for the comic. So let's talk violence.
There are two basic ways of looking at the level of violence in a comic. The first is your audience. For comics that are interested in younger audiences, the so-called "family comic", you usually want to avoid violence; it just doesn't really fit with the genre. Although one could argue that strips like Garfield would only improve if there was some bloodshed, in general seeing a family comic with violence would just feel wrong; although it is no doubt a fun concept to think of Charlie slapping Lucy around because of a certain football incident, violence simply does not work in that genre. The same applies if you want to appeal to an older crowd; comics are seen as an escape from reality, including the all-too-real issue of violence. On the other hand, if your target audience is adolescent, then go for it; violence has a visceral appeal that appeals to the crowd, both in its rebellious and that life is cheaper than the adults say it is.
The other is whether or not violence works for your world, even if that world is a subset of your usual world. Consider Wolverine's World versus that of the X-Men in general; Wolverine's is far more violent, with characters having no problem killing, maiming, or otherwise injuring each other. This is because everyone can heal, and those that can't are just too weak to survive. Life is cheap, and this is represented through the violence; it works rather well to differentiate it from the Marvel Universe in general where, even though there are lots of fights, there are rarely injuries. When someone shows up with a shiner or we see blood fly, it is a Major Event, and noted. Life is precious, important, and violence is thus something that really doesn't happen.
I'm obviously not saying that there should be no violence whatsoever, or that every fight needs to result in massive bleeding. You as the writer need to determine how violent the world is, and why; just like any other element you need to decide if you are going to have it, and what its absence or presence says about your world. So have fun with it; just have a reason for it.