I look at it like this: Both can be pretty vicious, but commonly they are so in different ways. Men are likely to physicly harm you if they are vicious bastards, while women are more prone to attack you psycologically, to destroy you from the inside.
Of course, this is a generalization and there are so many exceptions to this that I wouldn't present it as a rule, but this is what seems to be the most common situation.
Females without a doubt or more vicious, touchy and emotional than men are. This is part of what makes us sexualy ravenous for their attention. Sometimes I wonder what that says about our gender. :3
Men are naturally vicious by nature, but women can be vicious by choice or by need in order to defend themselves and those they care about. Messing with an angry woman is never a wise move.
Okay, it's often easy to say men are vicious But women are two-faced, manipulative, vain and selfish, not to mention WAY too easily offended and often pretend to be upset and behave like children just for attention, but it's hard to catch them at it. Also, if they can bitch about men who just want sex, which just seems petty considering they get over it so easily, doesn't that give men the right to complain about women who use men to boost their ego? I know not all women are like this, but I'm just telling the truth.
Overall, women are more vicious than men. Just sayin'.