The first time we saw Raidou was in the original, 1996 arcade version of Dead or Alive. Here, the dark lord returns to the DoA universe in the form of a modified cyborg, who is now more powerful than ever before.
This time he utilizes a new and modified Mugen Tenshin Ninjutsu fighting technique that allows him to copy the styles of other fighters. One of his best move sets is the throw combo, which uses counter-clockwise motions that can break any defense mechanisms.
Outside of player-to-player fights, Raidou doesn't disappoint in DoA 6's story mode either; he is one of the most overpowered antagonists in the game.
But DoA games do have a long history of extremely hard bosses, so it isn't really surprising at all.