In Phantasy Star 1 my favourite enemy would probably be on of the dragons, Probably the white ones.
In Phantasy Star 2 my favourite enemy would be the Fiend.
In Phantasy Star 3 my favourite enemy would be the Khalidah, her attack power makes fights so fun.
In Phantasy Star 4 my favourite enemy would be the ImagioMage's, they make fights so fun with all the spells they can cast.
So what would yours be ?