simple trophy, just beat the game on standard difficulty. i tried my best to speedrun through this playthrough but clocked in almost 20 hours. (not very fast, i know.)
to save time and avoid what i did; make sure to get ars arcanum at level 42 which will honestly destroy every boss in the game except for marluxia's 2nd and final form.
the reason why you want this ability as soon as possible and what makes it so legendary is because it only requires any attack card with a mere value of 1-6 plus you get to attack up to 13 times every sleight you use with that ability. awesome!
another thing you want to do to save time, is clear 1-2 rooms per world to make sure you have enough map cards to get through each world and never run out. so to recap what i suggest when speed running through the game if additional playthroughs is the only thing you have left is to:
1. get to level 42 asap and get ars arcanum. 10-12 decks should be more than enough, also put in a cure/ether card just for good measure.
2. go to agrabah as soon as possible and defeat jafar to get his card which let's you deal consecutive damage to bosses without them breaking your cards, though it's still possible but unlikely most of the time.
3. clear minimum 2 rooms per world to get enough map cards and to quickly run through the areas ignoring enemies you don't have to waste time on.
4. for marluxia's 2nd and final form, put in as many high cards as you can along with a minimum of 4 zero cards, some cure and ether cards. he's very weak to physical damage and you don't have to use any sleights on his last two forms if you play it smart and break his sleights with zero cards when necessary.
for example: if you're about to run out of cards and you want to manually refill your deck, refill it as much as you can untill he's about to attack you with a sleight, then quickly scroll to the back of your deck and put out a zero card to break his sleight, then return and continue where you left off refilling your deck. this way, he can litteraly not do you any harm and it works the same way for when you want to heal safely.
a good example is if you have a cure card of a value of 6 which is not very high consindering he got 7 and 8 value cards most of the time meaning he'd break your cure card before you have a chance to heal yourself, you want to rest on a zero card in your deck, wait till he is about to attack you, regular or sleight, doesn't matter, use your zero card then quickly scroll back to your cure card and use it. if you're fast enough, you're able to heal before he tries to break your cure card and sometimes he even manage to break it at the same time you're healing but you still get healed.
let me know if you need any further help with this or hints/tips and i will provide it.
message me on psn or on here.