Star Ocean: Till the End of Time

Every enemy in that dungeon save for the Magma Man has 320 DEF on Galaxy. Make sure Cliff and Albel have 321+ ATK and you're good to go. A couple of enemies resist Fire here so Hammer of Might will always be doing no damage (or if your character has a weapon with Adds fire element to attacks on it).

Ways to get around their DEF:

Cast Power Up with Maria or Adray (boosts ATK by 1.5).

Cast Acid Rain with Adray (lowers enemy DEF by 30%; sometimes fails with no visual or audible cue).

Update Cliff and Albel's weapons (you can find a 300 ATK sword for Albel called Steeled Earth in the Mountains of Barr, just a few screens before the cave where the Blue Dragon Zombie resided---there's a lone Feral Dragon on the screen with that treasure). You can find Damask Gauntlets for Cliff in the Lava Cave itself, which give 200 ATK to Cliff.

Symbology ignores DEF, granted this won't be very effective since Symbology damage is poor and these enemies have plenty of HP (MP is their weakness). Try shatter kills with Ice Needles or cancel chain some of Adray's magic.

Bombs ignore DEF, and even weak bombs like the Tricky Duck Bomb can destroy mobs here as the enemies have fairly low MP.

You could also just ignore these encounters entirely; they aren't a good judge of your characters' Levels and stats, and nowhere else in the game do such high DEF enemies appear out of nowhere (okay, there is one enemy in a dungeon that has 900+ DEF where your characters may only have 600-1000 ATK weapons, but it's easily bypassed).

That's the Urssa Cave Temple enemies, not the Lava Cave ones.