in my dream there was a guy going aroung beating people up- he was a karate master so could not be beaten. He came through our back door into the kitchen where my sister was and i came out and tried to punch him which didn't work so i grabbed a knife from the kitchen and stabbed him and slashed his throat. Then i woke up really freaked out. When i got back to sleep the dream continued. The guy was still alive and acting like he had brain damage. We were in a pub and he walked past and said hi, then as he was leaving he turned to me and said 'watch out'. Then i wokeup again.
What could this mean??

Dreams are expressions of your feelings about your waking life at the time of the dream. The setting of your dream (your kitchen), suggests that your dreams is about someone who is either in your family or has a relationship to it. The meanings of the symbols in your dream should help you identify who it is, what it's about and why you had it...

attacker: dreamdoctor.com/dream-dictionary/definitions/attacker.html
can't hit: dreamdoctor.com/dream-dictionary/definitions/can-t-hit.html
hit: dreamdoctor.com/dream-dictionary/definitions/hit.html
fighting: dreamdoctor.com/dream-dictionary/definitions/fight.html
knife: dreamdoctor.com/dream-dictionary/definitions/stabbing.html
cutting: dreamdoctor.com/dream-dictionary/definitions/cutting.html
throat: dreamdoctor.com/dream-dictionary/definitions/throat.html
threatened: dreamdoctor.com/dream-dictionary/definitions/threatened.html

Without knowing what was going on in your waking life it's hard to say who the karate master represents, but it clearly someone you feel has strong skills and powers against you and your sister... perhaps your father(?) The fact that you slit his throat suggests that you want to silence him. The good news is that you know you can overcome him. The bad news is that he doesn't die or go away; he remains a threat.

Once you identify who it is in your waking life, you can take steps to protect yourself.

Good luck!