Day eight!? Damn, that sucks. I should point out that you'll never get it doing what you're doing. Why? Well, Hammer of Might, a Fire-elemental skill, hitting Fire-weak creatures will only ever do damage that's even since damage is doubled against creatures weak to an element when attacked by said element and said doubling is applied last in the damage bonuses calculations, as far as I'm aware. That's why you keep seeing 77776's and 77778's, yet no 77777's. There is another strategy that will work (eventually). I believe it involved petrifying the Red Dragon enemy on L201-210 of Sphere 211 and then attacking it over and over with strong attacks that deal damage in the region of 77777 (you'll need to find a setup that let's you achieve that), while your other party members constanty attack it with Earth-elemental weapons to heal it (it absorbs Earth damage). That way you can keep attacking it without killing it until the trophy pops it. I've not tried it myself but many other people have got it to work so you should give that a go.