I reckon Edea was portrayed very nicely in her introduction just before she kills Deling. That famous FMV of her walking through the door with help of magic has stayed with me all these years. She's shown to be calm and composed, yet undeniably evil.

I think Adel could have benefited from a contrasting angry and psychotic persona (instead of the 'nothing' Square gave her). She could've had a big speech of her own like Edea did in Deling City or like Rufus did after Sephi kills his old man, but I agree with everyone else in saying that Adel could've been developed better.