[Blarg]

Well, just because you're not trained in martial arts doesn't mean you aren't athletic or don't have good timing.

Your reaction speed will rarely be anywhere near what a trained fighter's will be, though, nor your initiation speed(ability to start a movement off). Still, one good blow could do a lot of damage if you weight 3x what your enemy does.

But a blow has to hit to hurt. It's quite possible to hit someone a few times before they can hit back. If those hits are to the eyes or throat, that can be enough to end the fight. Maybe the groin. All those targets are hard to hit on a wary opponent, though, and you can actually fight through groin hits.

There's always a chance for anyone to win, but needless to say, you'd have to have a lot more skill and luck on your side if you were tiny. When you say "skill," there are such huge gradations even between very accomplished people that it would blow your mind, it's hard to even imagine what skill means, in a way. There ARE 100 lb. guys who are incredible fighters. The most famous fighter in Hong Kong in the 50's, and we're talking about street fights that were known throughout the colony, reported in the newspapers, and sometimes even involved weapons AND multiple opponents, weighed 100 lbs, and he was never defeated in over 50 fights. A guy like this could probably do it with little worry. But you probably don't bump into a whole lot of guys like that in your whole lifetime, if that.