Ok it’s seems the 180lb guy was the one who started the fight with the first punch! BUT let say u were about to fight him…maybe cause his size and his words…the 300lb guy was provoking u…how would u have stopped him…I have thought about this lately…and I don’t see how other than to hold on for dear life! And hope to god I can escape his onslaught!
I weight 270-275, so thats not such a great advantage he has 
ANSWER:
hit him as many times as it takes to stop him from being a threat.
what if u were attacked by the HOCKEY KILLER???
I would Puck him up!
Mistakes were made on both sides.
If I weighed around about 150 I would never have opened my godd*mn yap in the first place, or never took the first swing at that huge bear-like guy who tops out at 350. Firstly, because I’m a better MA than that and know my limitations, secondly because I’m a MA period. It’s not within my nature to go seeking confrontations, no matter the circumstances.
That aside, what would I do if some guy came at me and he weighed two hundred pounds more than me? (Which would put him right at 420.) Easy. I’d outrun the fat b*stard. I would NOT get into a slugging contest with him.