MY last characters are usually Magus, Ayla, and Frog.
Generally Magus over Crono because I wait until very last to go back and save him if I decide to do so during that play through. Frog and Ayla because they're both strong hitters and they can double tech AOE heal when needed on the last boss. With the two of them the right bit goes down in a single turn between Cat Attack and Leap Slash then Magus does over 2000 damage with Dark Matter on the right bit. Ayla Triple Kicks the right bit for more than that and then Frog will do over 1000 damage with the occasional elixer to get Alya's MP back up.