Lightning in XIV

[Keyln]

AFAIK the only one who is the exact same character in multiple ff games is Gilgamesh

Well, Cloud has been in Final Fantasy Tactics too, and there's Kingdom Hearts...

But the only character to make multiple appearances is Gilgamesh, and he's appeared in V, VIII, IX, and XII. (I don't count XI, because that's just a character named Gilgamesh, but not THE Gilgamesh).