In Final Fantasy

I always beat the game with 2 fighters, a black, and a white mage.
After beating it I always try to throw a ninja, thief, or red mage in the mix, but can never find the right combo.
Now, I have read the guides on how to beat the game with 4 red mages, but I am looking for the most effective team that includes one of them (ninja, thief, red).
I am presuming that it would be most easily done by replacing a fighter with one of them. But want to know what you all have to say.

Also, which character becomes the best after talking to Bahamut and 'growing up'?

I always use the Fighter, Red, White, Black Mage line-up. It's always worked for me.

As for the Bahamut scene, I'd say that the Thief becomes pretty cool after the event. As for most POWerful... I'm not really sure.

The best line up inmy opinion, is a fighter, black belt (don't equip him with armor or weapons), black mage and white mage. The reason being is that you need an offensive and defensive set of wizards, RED MAGE SUCKS cause he can't get high black and white magic spells. The fighter of course cause he can handle all the good weapons like the Xcalibur. The black belt cause he can hit harder than the fighter sometimes and you don't need to waste money on him for armour and stuff like you would if you had another fighter. ALSO, the thief sucks, he's only good at the last stage once he gest that kick ass muramase sword. Thats in my opinion...and I have beat that game like 10-20 times, NES ROM, nes and gba versions of it.