He is strong enough to solo most enemies with genji glove and blitz. I've just been using him to kill 80% of the enemies for the last 2 hours of gameplay (just opened the gate).
Signed, FF6 noob.
Sabin started great, but stalls a bit in the late game.
Locke is the opposite, in which he starts fairly weak, but has one of the most powerful setups in the late game.
Interesting. What about Edgar? Is he worth keeping in the group or should I look to replace him later?
There are no character that are so bad that they are invalid choices. Even if some characters are a bit better than others at different points in the game.
Edgar is a decent choice. He is almost overpowered early on and fades a bit later, when his tools can't keep up with multi-hit attacks and magic. I think his best late game setups involve setting him up as a dragoon. He would be doing a lot of Jumping, because he can equip spears and they get a damage boost to Jump.
Sabin is basically in the same boat, but I think his Blitzes scale better. Raise him like you would a mage, since his blitzes scale on magic attack.
Locke starts a bit weak, but is one of the better units in the game when you have access to the Genji Glove, Offering, and Valiant Knife. A popular weapon to pair with the Valiant Knife is the Atma Weapon, but I think that's at abnormally high levels.
Terra is probably the best character all around. Celes is probably the second best.
You probably won't really replace anyone entirely, because very minor spoiler: the final dungeon has you control 3 separate parties to reach the final boss.