Ultra Despair Girls (UP)

This is one you won't get naturally. You will need to do another partial playthrough in order to defeat enough for this to unlock. Unfortunately, there's no in game counter so there's no way to tell how close you may be to the trophy. I'd estimate you'll be around 200 enemies away however depending on the difficulty you played on. Either restart the game from any chapter you like and keep playing until you get the trophy, or replay one of the later chapters such as 4 or 5 until you get this. You might be able to farm this in the factory near the end of Chapter 4, simply allowing the laser to spot you and taking the reinforcements out with any bullets you have, or when you run out of them, Genocide Jack. Just make sure to save a couple of bullets to take out the Siren Monokuma when you're done. I personally played the start of chapter 4 up until the Jack fight over and over. Just make to save at the temple before quitting and restarting the chapter. Also check A Vault for another grinding method, which isn't as fast but also gives you coins (as the enemies in the factory after getting caught do not drop coins) so you kill two birds with one stone.