While the strategy varies by title, these are the core themes of an Omega fight: Ultimate Defense:

Found in Ultimecia Castle, this is widely considered the game's toughest boss. Use items for invincibility and to spam Limit Breaks like Squall's Lion Heart Final Fantasy X: Located in the Omega Ruins

(like Cloud or Sephiroth) because their attacks often pierce Omega God's high defense. Boss Locations & Rewards Major Reward FFI (DoS/Anniv.) Lifespring Grotto (B20) Interdimensional Rift Omega Badge Omega Ruins 50,000 AP / 20,000 Gil Insomnia (Royal Edition) Rare Metal specific walkthrough

The phrase "Ff Fight Omega" most likely refers to the legendary superboss (and its variants like Omega Weapon) found throughout the Final Fantasy