Nice thread, here are my picks: I report the rarity as the moment of writing.
Ape Escape 2: 6.00%
Way too low: besides some misc easy Trophies, the others are all story related, and the only ones that may be a little tricky require you to beat the game 100% by capturing every single monkey (Not required to beat the main game itself), and then to do it once more by using another character (Gameplay-wise, nothing changes). Considering that the game is nearly 20 years old, that it really is not a difficult one, and that is not so long either, I think it's way rarer than it should be. It should be noted that the Trophy requiring you to beat the game 100% for the second time is glitched, but considering the existing workarounds (PS+ Cloud Saves or beating the game for a third time as I did), I still believe that 6% is ridicolously low. 13-14% should be fine for me.
Dragon Ball Xenoverse: 3.41%
This one should be even rarer: there are two Trophies that are basically RNG and require you to beat every single Parallel Quest for multiple times, until you obtain the desired Special and/or Ultimate Attack: wheter they drop at the 1st try or at the 487465th try is completely random, and there are a total of 55 Parallel Quests... There is, however, a DLC that sometimes changes the RNG in your favour, and you can use it to your advantage and attempt the Parallel Quests when you are told that the chances of getting the desidered attacks are higher; however, it's still really tricky, because in order to activate your "Parallel Quests luck", it may take you one minute just like it can take you one hour of going back and forth from the HUB to the Parallel Quests menu, it is RNG itself; also, not to mention that after you have bought the DLC, in order to activate the luck RNG increase, you need to level up your character to level 95, which is a huge grind and takes hours and hours of grinding. And in the end, even if you are told that the chances of getting the desired items are high, you may still get nothing from the Parallel Quests. So yeah, this should be a 1/1.5% rarity Platinum, the players who got it before that DLC was released should stop Trophy hunting and win daily lotteries.
Fall Guys: Ultimate Knockout: 1.37%
Another rare Platinum that should be even rarer, and the reason is simple: a lot of players cheated on the Infallible Trophy using the exploit. Considering, however, that there is a huge gap between the earners of the Platinum and of the Infallible Trophy, likely formed by very lucky/skilled players who have no interest in Trophies and got Infallible in the very earlier days of the game when almost everyone was bad at the game, I think that the Platinum should be rarer but not that much: I think 1.15/1.20% could be fine. Not that much, but I still wanted to say it.
Jak II and Jak 3 (Ps4 Versions): 49.69% and 35.35%
It is possible to obtain these two Platinums in few minutes each by using debug mode, and that obviously inflated their rarities due to players buying these two games just to get easy Platinums. To have an idea of more likely rarities, the Ps3 and PsVita versions of these two games are at 18-11% for Jak 2 and at 21-13% for Jak 3: considering the difficulty on the games themselves, I think that they are fair rarities. Not to mention, however, that it is still possible to obtain the Precursor Orbs collectable Trophies by using a glitch: it takes some time to pull it off, but it is way faster than actually finding/obtaining them. If it wasn't for that glitch, the rarity would surely decrease even more, at around 6-7%, expecially considering that some of these Precursor Orbs are missable.
Ratchet & Clank: 27.29%
Similar to Fall Guys, every Trophy is not hard to earn besides one, that requires to obtain a total of 1.000.000 Bolts: it has never been confirmed but, by judging by the Trophy icon, it is likely that the Trophy required to get only 100.000 Bolts, not 1.000.000, and that they made a mistake that was never fixed. Getting 1.000.000 is, to say the least, pure uthopia, and to actually get it you either had to beat the game multiple times, farm the same sections of the game for countless hours, or exploit the Trophy with a glitch while being away from the console. And even by considering the least painful option (Grinding away from the console), it takes various hours, and should give you an idea for how problematic the Trophy was: a never intended amount of Bolts to be obtained thanks to the exploit of a never intended glitch. I don't understand how this Trophy is just slightly rarer than any easy Skill Point related Trophy of this game, I think the Platinum rarity would be fair if the Trophy actually required to obtain the 100.000 intended Bolts. Platinum rarity should be around 15% to say the least.
Sound Shapes: 27.02% (16.99%)
Considering how most Trophies are extremely easy to obtain thanks to guides and that this game can be stacked for multiple times, I don't understand how it is not in the 80-90% Platinum rarity range. Apparently, everyone who wanted easy Trophies was too busy getting Jak 2 and Jak 3 Platinums
Yeah, the title of thread is "Give A game [...], I got too far