Its actually simpler. This is strictly in the ball python world. Hypo is lacking some black/dark pigment. Ultra is lacking all black/dark pigment.
In the real world Melanistic is all black, a reverse albino if you will. Hypomelanistic is missing color, or albinoism. I guess if there was a real Ultramelanistic animal it would be clear? lol not sure
There is a Melanistic North Western Garter snake that is all black.