Lets Make a Game Together

(((((((100 x 2/5) + 2) x (2160 x 7368/50)/1)) + 2) x 2 x 1,5 x 1,5 x 4 x 1,5)
=360,949,532 seems to be the maximum amount of damage.

It is that Shuckle vs Yanma, with the max rollout defense curl, mimiced from opponent, helping hands and flower gifts flying around, tricked choice bands too. that is quiet a lot of damage if you ask me.

edit: even then, kaphotics (a smogon researcher, also active on bulbapedia) still has not given the final answer on that one. Seemingly difficult to calculate ^_^.