This wouldn't unlock for me when I changed the time per round or the number of rounds, or when I changed any of the participants other than the one I was using, so leave everything on the default except for swapping out one player for a Legend. I chose Jeff Bagwell to sub in place of Pete Alonso. Play on Easy and use Classic hitting controls. Just as the pitch is crossing the plate, press down on
to swing. It may take a little bit to get the timing down but in general I felt like I had to swing late, so if you're early on everything and pulling it foul, try letting the ball get closer to you before swinging. You'll likely need to hit over 20 per round to be able to win as a couple different batters like Acuna and Vlad Jr hit 20 in my derby. Once you get a rhythm going 24-28 should be easily possible in 4.5 minutes (30 seconds extra for 2 long HRs which will almost definitely happen).