Level 4 Limit Breaks
Cloud: Omnislash
Fight in the Battle Arena at Gold Saucer until you get at least 32,000 battle points. The points can then be exchanged at the Battle Arena for the Omnislash Limit Break.
Barret: Catastrophe
Revisit North Corel once Meteor has been summoned and speak to the lady in the middle house on the west side of town. She'll give Cloud the Catastrophe for Barret's Limit Break.
Tifa: Final Heaven
After reaching Nobeilheim, take Tifa to her house and play the song from Cloud's flashback at the Kalm Inn. The song is: Do-Re-Mi-Ti-La Do-Re-Mi-So-Fa-Do-Re-Do, or X, [ ], A, R1/L1 + A, R1/L1+ [ ], C, [ ], A, R1/L1+X, O, X, [ ], X.
When finished with the tune, press Start and Tifa will say she has the sheet music for that song. Inside the sheet music she finds a note and her Final Heaven Limit Break.
Yuffie: All Creation
Yuffie receives her All Creation Limit Break for defeating Godo, her father, at the top of the Pagoda of the Five Mighty Gods.
Cid: Highwind
After getting the submarine, locate the crashed Gelnika off the shore of the Gold Saucer. Inside the cargo bay, you'll find Cid's Highwind Limit Break.
Aeris: Great Gospel
Speak with the sleeping old man near Junon when you've fought a number of battles where the last two digits of the number are the same. He'll give you a piece of Mythril that can be exchanged for Aeris' Great Gospel Limit Break, which is in the small box.
Vincent: Chaos
After acquiring the submarine or a Gold Chocobo, you can reach Lucrecia's Cave, which is located behind a waterfall at a lagoon in the Nibel area. Visit the cave with Vincent in your party during Disc 2. Then during Disc 3, revisit the save with Vincent in your party and you'll get his Chaos Limit Break.
Red XIII: Cosmo Memory
To get Red XIII's Cosmo Memory Limit Break, you must defeat the Lost Number Boss in Shinra Mansion. This requires opening the safe on the second floor of the house.