Please do not put up with this. My ex used to do this to me, mostly when he'd been drinking. It never happened until after we were married, and I had told him many times while we were dating that I consider that word very hurtful.
He only ever apologised once and then a few days later he changed his tune to say I had pushed him to behave that way. It only got worse as time went on and at one point he actually said out loud that now that we were married he could do what he wanted because it's not like I would ever leave (joke's on him!). Be thankful that your fiance has shown you who he is now, before you end up marrying someone who doesn't deserve you.
I too grew up in a household where verbal abuse was normal. The penny didn't drop for me until I was visiting my in-laws and BIL called his wife (who wasn't there) a bitch in front of everyone, included his parents. I was shocked but realised no one had even batted an eye. It was clear that speaking about your spouse this way was acceptable in this family so I knew he would never change.
I also started to think back to some stories he told me about his exes when we were first dating. Justifying terrible behaviour by saying they were unreasonable, crazy, etc. A few years older and wiser I realised he was probably twisting these stories in the same way he justified his behaviour towards me, and that 10+ years after dating these women he still hadn't grown up.
If you think about it OP, I bet there is more than just him calling you a c*nt or telling you to fuck off. Those alone are reason enough to leave (and are emotional/verbal abuse) but I'm sure there is more. Is he dismissive of your feelings/concerns in other areas of your relationship or put you down?
It was a really hard decision to leave my marriage, but I have since met the most wonderful man who is supportive, kind, generous and would never speak to me the way my ex did. I tear up thinking about him sometimes because I never thought I would find someone who made me feel so loved. Don't settle for less than you deserve.