>>76316867 (OP)Well, just plain size isn't enough (think about manatees), but people practically always mean some combination of size and strength.
"Size vs skill" is a kind of an oversimplification anyway. It's usually debated by insecure martial arts practitioners as a form of copium versus other (usually strength) athletes.
If we'd change the terms into "natural ability VS rehearsed skills", then we'd be more to the point.
Like, if we'd somehow be able to give a person a 5-10x faster reaction speed than that of a normal human, that person would be likely to win in a boxing ring against almost anyone because all the opponents would be basically moving in slow motion in that guy's perspective.
Also, if, other things being equal, you're big and strong enough that you can just one-handedly grab your opponent and slam them to the ground, then you have an obvious advantage, even against a more "skilled" opponent. Like, if a 6-year-old kid would go against someone like Eddie Hall, even if the kid "knows kung fu", it won't matter much when any contact will basically lead to a one-shot victory for the bigger guy.