Lavos

Part 1

Lavos Shell

Hp : 10 000

When you start the fight, Lavos will use the attacks of the following : Dragon Tank, Guardian & Bit, Heckran, Zombor, MasaMune, Nizbel, Magus, Azala & Black Tyrano and finally Giga Gaia. Defeat these forms as you did before, they have the same hp they used to have.  After you beat them all, Lavos will roar and start attacking your party, use whatever combo you like but make sure you Cure the member that gets hit by a needle attack, it hurts alot.
 

Part 2

Hp : Head 20 000
Left Arm 8000
Right Arm 12 000

Simply use your strongest attacks to kill the arms and cure often, the Laser Beam is painful. Once the arms are gone, concentrate all attacks on the head.  Cure if needed.
 

Part 3

(image of Lavos Bit unavailable)

Hp : Left Bit 2000
Central Bit 10 000
Right Bit 30 000

Start attacking the left bit with physical attacks, once it dies concentrate all attacks on the right bit, use a mega-elixir if you feel the need. If the left bit is revived, repeat the process until right bit is killed. Triple Techs work best. When the right bit dies, the others will die too.