FD or FD god in the original animation. I believe the character is a self-inserting character of the creator himself which is quite a common trope in any fan media of that time.
Technically, a self-inserting character is not totally bad, like Luke Skywalker from Star Wars or Hermione Granger from Harry Potter or some works from Dante. But due to the nature of the character itself, it leads to a pretty bad writting in general, like most self-inserting anime main character. Only a support self-inserting/extra character can be generally good.
In the animation, FD is mostly defeated in the end even he is extremely good. I believe the role of the character is to kill off any remain characters so the animation could end quicker before transfer the end role to a selected character (like SWAT or The Pro).