You get all the energy out that you put in, and that includes the rest mass of the particles (times c2, because our units are stupid) plus their kinetic energy. So, if you didn’t have to spend any energy to make the bulk masses of those particles and/or get them up to whatever speed they have, then you “win”.
We’ve been down that road, though. If you want to revisit such speculation, I’m happy to, but as a starting point you might want to revisit the problems we discussed last time. To summarize that discussion (wow, ten years ago): one can’t arbitrarily manipulate language in a story-like fashion and have it make sense as a model of physics. We understand the properties of antimatter extremely well. We make it everyday and study it everyday. It’s not something that acts in any quirky way. It’s acts just like boring ol’ matter, aside from one nuance in the weak force of the Standard Model that means matter and antimatter interaction rates can, in some specific cases, differ.
Yes, I was referring to low-KE (essentially at rest) annihilation. The proton and antiproton together represent 1.9 GeV of rest mass. A pion has a rest mass around 0.14 GeV. In principle there’s enough oomph in the annihilation to make thirteen pions, though such a crazy final state would be heavily disfavored for phase space reasons. More typical is half a dozen or so, with some energy left over for outgoing pion kinetic energy. But there are loads of others mesons light enough to be produced in the annihilation, though of course without as many at once.