Apparently you only get the good ending if you go through the entire game without commiting any "Ally Murders." It's not like i was intentionally going around gacking my own party, but there must have been at least one time when someone accidently got caught in the crossfire of a large spell or something and got nuked.
So now i need to go through the whole game again to get the best ending, but that's not as bad as it sounds since there's a "New Game+" option. I did a little leveling on one of the maps that seemed designed for that purpose and my level 120 Laharl made the last few stages of the game a cakewalk, so the first 90% of the game will be trivial the second time through. The only question is how much more time do i want to spend leveling people and items and getting alternate endings before i do that.
I'm wondering if i want to stick it through till i get the good ending or take a break and start up Breath of Fire Dragon Quarter or Wild Arms 3.