"Only" supersonic.
You know how Saber runs up the side of a building in her fight with Medusa? Speed Demon can do that with ease. He can also run on water without any blessing from the Lady of the Lake. So yeah, he's far, far below the Flash's level, but he's still a speedster - someone supposed to be hard to hit. And even then, Spider-Man has fought him and his Sinister Syndicate buddies all at once, and won.