The best way is to get Crono's Def and MDef to the max and keep using Ice sword 2. The first fight inside Lavos Destroy both arms and cast haste/shell (Can't remember the names) on Crono and Marle then hammer away with Ice sword 2. For the second fight keep using Confuse on the left thing , then Ice sword 2 on the center one until the right one lowers its defenses then hammer away at it (Cant remember whether to use magic or physical attacks). I was only at Lv. 42 when I beat him with Crono and Marle. Don't overthink the fight it's really simple.