No offense to Magus, but seriously, I think the danger of a near omnipotent planetary parasite is a little worse than the death of one comparably measly little sorcerer.
I just love how Nack, Samus, and that space pirate are totally unaffected by the sheer horribleness of this news because they have no idea what Lavos actually is, while everyone else is just freaking the HELL out.
To put things in perspective for those unfamiliar with Chrono trigger but familiar with Lovecraft.... Lavos = Ctuhulu - tentacles + multi demensional existence + time travel.
Lavos is not Cthulu in any sense, for one thng Cthulu didn't come to Earth alone, for another he and his companions raped the entire planet, then, out of boredom, decided to take an eternal nap. Kavos crashed onto the planet, burrowed into the core, began feeding off the various forms of energy on it, manipulated evolution to maximize his energy consumption, surfaces in 1999, wipes out virtually all life, makes a bunch of babies, and eventually would send them out to repeat the process elsewhere.
Lavos is not he whom you should fear, the true danger lurks within one's life, until that being is gone, his counterpart(i.e. Lavos) shall revive...and I think Sephiroth while typing this
Lavos doesn't return after being killed, this comic takes place BEFORE Lavos is killed, he dies nine hundred ninety-nine years into the future from this comic. They already explained this.