I mean - consider for a second that we currently have the most comprehensive martial arts practice in all of history, with the largest humans, best sports science, and all that.
Any top UFC fighter from the past decade could probably beat the fuck out of anyone ever before the year 1980. Isn't that wild? Dudes who have (probably) watched Rick and Morty could beat the piss out of Alexander The Great or whoever the fuck. And it wouldn't even be close.
Biting and eye gouging is banned of course, but even if it wasn't, Brock Lesnar isn't letting you even get close to that. I mean, speaking of Brock, even big pro wrestlers - medieval blokes would shit their pants on sight if they saw Scott Steiner going freakmode off the roids. Perc Angle. Big Show - like what - he's a literal giant.
But what about Mark Zuckerberg? He's a big guy. He does his MMA. I think give him a month to train and send him back in time. Hate to hand it to him, but he would crush.
no weapons in the cage sorry
Guns are interesting too because like a half way decent competition shooter with a 1911 handgun or 1866 lever gun is probably going to go John Wick on people of those time periods due to modern techniques and training.
But there's probably some Prussian guy who can shoot 4 musket shots a minute or a frontiersman who hit a bullseye with black powder smooth bore with no sights from 100m who will annihilate a modern special forces guy if muskets are involved.