Some enemy attacks can inflict the “Bound” status, which prevents the character from moving or acting. Defeating an enemy that has a character “Bound” will free them, as will hitting said enemy with a powerful attack like “Braver” or “Omnistrike”. You can get this as early as Chapter 1, as Sweepers have a stomp attack that can inflict “Bound”, but it’s easier to obtain from the Gorgers in Chapter 3. Once Tifa joins your party, just run around Scrap Boulevard until a Gorger hits somebody with “Feast”, a leaping attack that inflict “Bound”. It should be a simple matter to kill the offending Gorger and earn this trophy.