Streetfighting as a whole should be avoided. I have been in advanced boxing classes for a long time now, and while i know boxing is much different than streetfighting, it also shows you what kind of punishment some people can take and deliver.
Heres my best advice: To win a fight with most anyone (experienced fighters are an exception) You need to be able to hit EXCEPTIONALLY HARD.In The heat of the moment during a fight, both parties are usually unnafected by pain. So you had better be able to hit hard enough and accuratley enough to cause real physical damage. Broken ribs, knock them down, rattle their brain so much from a punch that they physically cannot continue. This is unrealistic punching power for most people.
You also had better be smart, quick, caculating and unheasitant. If youre going to fight, youd better do it, dont second guess yourself as the knife digs into your gut.
A lot of people like to say something along the lines of "well in a fight everything goes black". True for most, but the best fighters are the ones who remain calm and watch their opponents every move. If hes throwing wild, easy to dodge haymakers and youre calm and weathering/ dodging every hit, eventually (soon) he is going to eithier be word out and easy to take out, or youre going to catch him with one vicious punch he isnt going to recover from for the rest of that fight.
You also need to remember that even if you can hit hard enough to knock someone out with a bodyshot, a bat to the head and laugh, or dodge any punch, that youre still human and getting shot in the face will still kill you. Getting stabbed will kill you. Held down and strangled will kill you. Kicked in the head by 30 people for an hour will kill you. Being run through with a knife while youre beating his buddies ass is not that unrealistic of a scenario. So, just be careful out there.