Say what you want, but size and strength is an advantage in a fight. Fighting is movement, and if movement is aided by a large amount of horsepower, that’s ... an advantage.
Size, well, providing it’s capable of even modest mobility, can allow one to absorb considerable punishment. Like a battleship or tank.
As far as “gassing out”, largely this only matters in combat sports.
In all my years being involved in, and being witness to, altercations, I’ve never seen anything of a serious/potentially dangerous nature exceed 30-45 seconds. Usually it’s broken up much before this. And if it isn’t, and the scrap continues, each combatant has very little skill, athleticism, strength, or scrapping ability.
(If you have something, you’ll either “win”, or inflict damage, within this window.)
They’ll just gradually give up, equally, and be on their way. Spouting a few closing “fuck-you-goof” remarks.
If someone is dramatically larger and more strong/powerful than you, hopefully you can achieve a knockout or choke-out, otherwise you’ll likely be injured.
Being a trained fighter gives advantage, just like strength and size.
Case by case.