What do you trade in the GTS to get Dialga on platinum?

Answer 1

Probably something really rare and hard to get and at a very high level, maybe even level 100.

Even a level 100 Unown might do it , because it may take about 5 hours to get all of the Unown in the Solacean Ruins, and seeing that they only know the move Hidden Power and cannot legiimately learn anything else, so few people want to stay in the ruins for 5 hours, and whenever I try to catch all of the Unown in Solacean Ruins, I am almost always there for about 5 hours, the last hour just waiting for the last 1 or 2 Unown to show up, and hopefully I will not faint them .

Because they only know that 1 move, few people probably want to spend a lot of time training them to get a level 100, especcially if they may be in a battle where their hidden power move does not effect the opposing Pokemon.

For example the hidden power takes on the electric-type attack

and its battling a ground type.

The Hidden power type depends on the Pokemon, but there is a man in Celadon City who will tell you which type of hidden power your Pokemon can have.

I have seen people offering a level 5 Magikarp for a level 70 or So Rare Pokemon or Even an Event Only Pokemon, which is really unrealistic, I think.