i once calced lv100 252+ choice band pure power fire-type deoxys-A using v-create in sun at +6 attack, on a lvl one 0- snover at -6 defense. the damage was nothing short of lunacy. i shall edit in the percentage later for those curious; it was at least a seven digit percentage. iirc i think it's the highest my friend and i were able to find. we got close with a few others, like solar power blast burn off the same deoxys with specs and +6 spatk, 252+ spatk etc, but nothing was as high. in fact, the same vcreate as above, but without the fire type (so you lose stab), was still stronger than the stabbed blast burn (because of more base power, and the advantage of pure power - double - over solar power - 1.5x). in some circumstances, you can get higher percentages if you calc against shedinja (obvious reasons), but the actual numeric damage dealt was higher on snover (again, for obvious reasons)
anyway i'd say this calc is nearly perfect, probably the best one out there. the only thing i find myself wishing it had was a reverse/swap button so i could compare obscure sets without having to manually reenter them all. everything else i can think of is already there
EDIT: whoa, i just realized my calc was not the strongest ever. i forgot to give snover dry skin. brb calcing again
EDIT: okay so level 100 deoxys-A, fire type for STAB, ability is pure power, in sun, 252 attack EVs, 31 attack IVs and adamant nature, @ choice band, with +6 attack boosts, uses v-create on a level 1 snover, ability is dry skin, 0 defense EVs, 0 defense IVs and hasty nature, @ no item (but only occa would really have an effect on the calcs), with -6 defense drops. the attack does not crit. this deals a glorious 8,744,512-10,287,664 (8.7 million to 10.3 million) damage, or 72,870,933.33-85,730,533.33 (72.9 to 85.7 million) percent. and for what it's worth, if we replaced snover with a shedinja (otherwise everything is the same), it takes 4,372,256-5,143,832 (4.4 to 5.1 million) damage. that's roughly half as much - no surprise there - but that adds up to a titanic percentage of 437,225,600 - 514,383,200 (437.2 to 514.4 million) percent.
anyway sorry if this is off topic but cmon guys, these calcs are crazy awesome
EDIT: that friend of mine was reading around and noticed a discussion on PO about shuckle with power trick, on its fifth shot of rollout (base power of 30*16 = 480). could probably hit harder. time to investigate!
i couldn't figure out whether rollout is affected by metronome or not, so let's take power tricked shuckle, cb pure power, 252+ EV and 31 IV at +6 attack. it's on the fifth shot of rollout - 480 power. it attacks a level 1 hasty ledyba with -6 defense, 0 EV and 0 IV. 15150972-17824672 (137736109.09 - 162042472.72%). OH yeah.