I've seen a few people mention how they found this to be rather difficult but it's actually extremely easy once you work out the mechanics behind this mini-game.

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2058736899

• Always back off from an opponent when they enter so they'll charge towards you, this avoids you accidentally punching them out of the entrance door and therefore disqualifying yourself because you stepped out of bounds. This can be very frustrating.
• Once they get close enough, run towards them and push them (B on Xbox 360 controller) to immediately stun them and open them up to your barrage of punches.
• Generally, you can just mash B from this point on with the majority of opponents in the early rounds.
• If they get a punch in or the upper hand, just repeat the sequence of running away and then running back into them with a push. You can also try countering with the A button but in my experience this proves to be very risky.
• Once you start getting opponents with weapons, it can become extremely frustrating as they tend to deal excessive damage rapidly. The best option for these opponents is to counter the first opponent with a weapon when safe to do so and use this weapon on the next 2 opponents to quickly dispatch of them.

This is something that may take a bit of practice and patience but once you get the hang of it, it's one the easiest things to do in the game and in my opinion, one of the funnest things to do as well.

I've included a video below to illustrate the above bullet points as best I can. Mimic this and you shouldn't have any problems.

https://www.youtube.com/watch?v=eBVdLevVQBw