I guess I should've expected this from an SNK boss but I was still pretty surprised and annoyed when I finally got to Mizuchi in arcade mode and with a 1/4 health on CPU 1 he still managed to destroy me over and over. No matter who I fight him with I can't seem to take him down. Does beating arcade mode unlock anything aside from an achievement, because at this point I think I might not even bother. He can spam his projectile attack so quickly that I can't even get near him, and he does ludicrous damage.

Well, yeah. Mizuchi is just a less powerful version of Orochi from KOF '97. And no, as far as I can tell there isn't anything unlocked by beating him