The skill levels say he's hacking. Not all of us are patient after all, and it's a game, so if that's what he wants to do to have fun, so be it.
That said: you're going to need to hack in a fucking ridiculous Flan if you want to OHKO, hell, even defeat, Twin Hibachis v2. I tried it myself with a Level 10000 Flan with bonuses invested in Attack (note that, due to how the stat mechanics work, levels are more important than skill levels, so a Level 250 character is still going to be limited regardless of how much Skill you invest in them), and a Skill Level 5000 in Attack, which gets me about 150,000,000 Attack+Magic. It's enough to OHKO ***WINNER***, but still deals 0 to Physical Hibachi v2 due to his 1,000,000,000 Defense (Forbidden Fruit/Laevatein will also deal 0 to Magical Hibachi v2 due to its 1,000,000,000 Mind, though you can kill that one with Starbow Break). You're better off hacking in a high-level Kaguya if you want to OHKO Twin Hibachis, since Hourai Barrage will ignore those defenses.