I just want to say one thing on this, and then just step back and see what can be said in response:
Lavos is an alien. He's not human. He collected human DNA at some point, and possibly absorbed the knowledge of, like, the entire species, but he was originally not human.
One more time: Lavos is alien.
So, here's my thought...how can human concepts be applied to a non-human entity? To attempt to make animals subject to our laws, rules, and regulations as if they were human too is simply impossible (for the reason of applying human concepts, as well as other reasons with nothing to do with Lavos or this debate here, I should imagine).
I will not argue Lavos's sentience, intelligence, or whatever.
I simply state that, as an alien lifeform, one that could have "grown up" so to speak on a planet where life is completely different than life on our own planet, developing in completely different ways, possibly having their own concepts of right and wrong (or, more to my thought, no concept at all of such a thing), we cannot apply our concepts to him.
Let me say that again. We cannot apply our concepts to him. So let's say that, yes, he did absorb all of our knowledge - that doesn't mean he believed we were right or even worth considering whether or not we were right on such possibly (to him) abstract concepts of "good" and "evil".
This is not to say he cannot process the concepts of good and evil - it is more to say that he could have easily seen them as human concepts. Possibly true for them, but not so for himself and his species.
I believe there is absolutely no way to classify his actions as truly "good" or "evil" unless one of us can actually sit down and have a conversation with the creature in some way. We do not know his perspective of things - we only see his actions, from the view of those trying to stop him, believing (perhaps in bias) that he is "evil", or at least must be stopped out of necessity.
Humans may be as they are because of his influence, but they are still human species, and Lavos is still of his own, completely separate species. The thought processes may be so different from one another as to...oh, I was going somewhere with this, but I lost my train of thought...
(This, children, is why you should never try to be epic at 7 am - if you've been up since 3 the afternoon of the previous day.)
Sorry about that. But I believe I've...well, said way the hell more than I intended to initially, but still have (hopefully) at least gotten my base idea out. I hope this wasn't said by any one else in any way, shape, or form, as I was sure before I'd started typing this up that no one had.
Let me just leave you with one last thought:
What if our ideas of right and wrong are wrong? Well, more appropriately, I suppose, to avoid confusion, "incorrect"?
We cannot absolutely prove anything on the concepts. We believe certain things, we think certain things, we say and do certain things - but just because we say or think or believe they are true, does that mean they are?
Mayhaps Chrono and that unnamed scientist in Chronopolis were right...
"Humans are such fragile, disjointed, imperfect things. Love and hate... Life and death..."
"...humans are, biologically speaking, unbalanced and half-finished. Internally inconsistent and disconnected, the human existence is plagued by contradictions. An incomplete species, torn between love and hatred, whose very being is self-contradictory."
(Oh, and, I snipped these from ZeaLitY's full game script of Chrono Cross at GameFAQs - thanks for making it, and I do hope you don't mind my using those two bits for this post.)
And finally, that bit about having a conversation with Lavos...not to go off topic, but, I think that'd make for a hell of a fanfic. What do you think?
(Edit: And just in case I shoulda said it before, since I forgot to: Yes, all the above is just my opinion, based on my own musings, and playing Chrono Trigger and Chrono Cross a lot, and such. Just. My. Opinion.
I say that so, like, I don't get flamed or in trouble or anything like that. >.>; That'd be bad. Especially as I'm new here. Yes...)