What is the fewest number of playthroughs to get all the trophies?

Solution 1:

It has been an old question, but I asked myself the same, so I looked for the information. Time to give it an answer. It is possible to get all of the trophies in a single playthrough in each game.

All the trophies have been made so that such a thing is possible. For instance, for Kingdom Hearts 2 Final Mix, there is the Critical Competitor trophy, which ask you to finish the game in Critical, and the Proud Player one, asking you to finish it in Proud mode. If you finish the game in Critical (which is an harder mode than Proud), it will unlock both trophies, so that you don't have to finish the game twice. So, for both games, just make sure to start a party in Critical difficulty, as Kingdom Hearts Birth by Sleep Final Mix also have a Critical Competitor trophy. For the other trophies, as long you make sure to achieve their conditions at the right time in the game, it is possible to do all of them in only one playthrough.

There are some guides which can help you to achieve such a run, like for instance this one, which also confirms this point :

All Trophies can now be earned in a single playthrough of each story.