Everytime Lavos would attack me, I would counterattack. These counterattacks would 95%(or around there) be critical hits. Even if Lavos heals itself, I deal more damage than it heals, so it gets done by no time.
...I hope this helps. :(
just get weapons and stuff that have a high critical/counter attack rate and you'll be fine.
Darn I should've never sold CT. >>; I would SO remember how to help you in this situation.
As far as I know though, doesn't Chrono have some techs that attacks three or more enemies at once? Lavos' body is consisted of three parts, so it'll attack all three and it'll probably make things easier then. And Like I said dude, Frog + Chrono double techs are freaking amazing. I spam them all the time. ♥
and that airplane pilot girl. ;___; god I forgot her name already but she's pretty badass too if you equip her with the right items/weapons. She isn't the strongest ever but she's definitely useful.
Aside from that, you shouldn't have any trouble with Lavos assuming you still do have Magus on your team. Magus' magic is freaking amazing. D: