I should say just to be clear that I don't think it is a word that should be used freely (ie, you shouldn't call your kids in with that word) but I don't think it deserves the title of 'most offensive' swear word.
Maybe I should explain why I don't have a visceral reaction to it. I think if you accept it is an offensive, misogynist, sexist word towards women and use it as such what you are saying is that to to be the owner of a c***, ie to be female, is something to be ashamed of and that to be a woman is the worst possible predicament to find yourself in (which reminds me of orthodox Jewish men who wake every morning and thank God they were not born a woman). I refuse to perpetuate that understanding. By you saying that c*** is an offensive and sexist term, to me, you are saying to be female is offensive. If you can't (or rather shouldn't) call a woman a c***, it's like inferring women are supposed to deny their womanhood by claiming that it is not part of them as it is such a heinous thing to possess.
However, if you divorce the denotation from the word, it's a completely different story. It stops being something strictly referring to women and with that said, jesus, it is a great word to say. It sounds aggressive and as Penny Red said, it is difficult to say without bearing one's teeth.