I don't understand why people couldn't simply enjoy debating the question becaust it's an interesting question. The demand of boxing don't produce the same sort of strength as wrestling, which a lot of noobs don't know and which is interesting in itself. But then you see videos of hardcore martial artists putting people on their shoulders and running up and down stairs / squatting / doing push-ups, etc. If you're engulfed in a hardcore training culture like kyokushin you're probably going to get pretty fucking strong.
And I remember a Black Belt magazine article talking about the journalist going for a run with Oleg Taktarov and gassed out after about 45 minutes... so then Taktarov put the guy on his shoulders in a fireman's carry and continued running. Can you imagine the kind of shape that man was in? Fucking unreal what comes out of certain countries and training cultures.
And, yeah, I would vote for Sumo for pure strength. They're basically two bulldozers sprinting at each other. Amazingly explosive.
But, for Christ's sake, I don't understand why people couldn't enjoy talking about the different training adaptations martial arts place on the body. That's a fucking fascinating conversation in it's own, especially when you have some cultures training wrestlers with maceballs and clubbells, others with calisthenics, others with simply bizarre ways to pick up external weights.
This was such a rich topic of conversation we never once needed to delve into the primacy of barbell training. FFS I think people on this forum enjoy telling other people they're wrong more than they enjoy learning about S&C.
Surely sumo develops the most. Wrestling and judo would be similar, but develop different areas. To put it crudely, wrestling probably develops more lifting strength, but judo much more gripping/forearm strength. That's an extreme simplification, but you get the idea.
Judo produces some unreal pulling strength, imo. The lats, the rear delts, the entire trunk when they start rotating to pull people. It's basically a sport of face-pulls.