First and foremost go to the arcade settings and change the difficulty to the lowest settings along with upping the health sliders and lowering the time to it's lowest setting. These will all make the final boss exponentially easier.
Most people suggest B.B Hood Or Anakris for this trophy. B.B Hood has solid projectile supports which help and Anakris has a move than can be spammed with triangle that keeps the enemy at bay. If you pair these two together and throw in the occasional hyper, it should make these trophies feasible enough. Sadly, this is the most annoying one as there aren't many good projectile spams.
Once you reach the final boss, simply guard for the first two phases. You'll win due to time out because he only has one health bar to your three. For the final bit, use ultras to help your cause and damage the boss but continue to block in hopes of winning by time out. It may take some time to learn his attack patterns, but it's much easier to just block his attacks than to avoid and counter them.