Fastest Horses In Minecraft. Currently / summon horse [x] [y] [z] [datatag] is what you want to use. But even in vanilla minecraft, it’s theoretically possible to raise a horse’s health above the maximum:

The black pegasus is a fireproof variant of the pegasus and one of the fastest horses in all of minecraft! You can also give your horse treats to increase the speed = The black pegasus is a fireproof variant of the pegasus and one of the fastest horses in all of minecraft!