Ohh right, that one. It's almost awesome enough to motivate me to do all that stuff to get it. Almost.
Take it from me, when doing it on Critical Mode, it actually kinda does feel like a genuine accomplishment. A right pain in the ass, but still an accomplishment.
Alright, and here's one final question. Critical mode is basically the same difficulty as Proud but the only difference is the HP bar limit, right?
As far as I know, not only do you have less HP, but I do believe that enemies hit MUCH harder than they did on even Proud. That one midboss you fight right before freeing Lumiere, Cogsworth and the rest was easy enough for me on Proud. On Critical, he WREAKED me so bad that I actually had to be rescued by Mickey.
Actually, Beast's Castle in Critical Mode (both visits) is pretty challenging since the damage output from the Heartless and Nobodies are really high for up to that point.
In the end, it really depends on where you are at on your playthrough. It's incredibly easy at the beginning due to the added 50 AP, but there are certain parts of the game that will test your patience. Just play strategically and you will manage to unlock that smexy secret ending.