Let's assume that somehow a hoofed creature became a carnivore. Since hoofs are inferior in every way for hunting animals, it make sense that the species would need to evolve to hunt better. Thus, if a hoofed creature evolved to be carnivorous, how would the hoof adapt to this?
Well, looking up "hoof" on Wikipedia, I found that it is
the tip of a toe of an ungulate mammal
And apparently an extinct ungulate, Mesonychid, was carnivorous and also had
four digits that ended in tiny hooves on all of their toes and were increasingly well adapted to running.
Regarding their diet:
Many species are suspected of being fish-eaters, and the largest species are considered to have been scavengers.
They are also considered to be related to cetaceans, some of which are carnivores.
So it seems like hoofed creatures can adapt fairly well to eating fish. However, the shape of the teeth is more important.
I've also heard that other ungulate species, like pigs, can be fairly omnivorous even if not truly carnivorous.
Right, firstly, animals have already done that, twice. First were the mesonychids, then the entelodonts.
The reason for this happening wasn't because hooves were better or worse, it is simply because the first big animals were hoofed herbivores/insectivores. The carnivores that rose from them simply kept the hooves that their relatives had.
Another thing to note is that, yes, hooves aren't great for holding onto something, your jaws are. Animals like the Mongolonyx had a massive head and huge jaw muscles, because their predecessors had them already. They would also have likely hunted in packs (herds?) as fossils from Mongolia are often found together. They also were not by any means primitive, as was found with creodonts (sarkastodon etc.), they had relatively carnivorian sized brains.
The mesonychids were actually very successful and survived all the way up to the early to mid oligocene, while creodonts went almost entirely extinct (though the Mongolian Hyeanodontids survived till the early Pliocene).
Mongolestes, the last known mesonychid, would have been a top predator, and it's genuinely not known why they went extinct, as they dominated their niches.
I have noticed that many people say stuff like the claw is the perfect weapon. Yes, it is good for gripping, but plenty of animals don't need it and many also don't use them to the extent that you would think (dogs, wolves, etc).
Nature has already had a go. They were called Entelodonts or Archaeotherium and were large pig-like creatures which became extinct about 16 million years ago. While not quite out and out carnivores, they were certainly capable of being the apex predators in their environment.
Regarding "hooves are inferior in every way", no they are not. Yes, claws are useful, its why Carnivores (as in members of Carnivora) have them. But if you've ever actually looked at a hoof, they are very useful weapons in there own right. Claws may slash, but hooves bludgeon, and as a result can kill much quicklier and cleanlier, especially if the hoof is uncloven. People have died from horse kicks.
I fail to see why a hoof is inferior for hunting. What it really comes down to is the hunting style and the preferred prey plus the terrain.
I can see a hoofed predator hunting it's prey by speed and stamina. It just runs the prey down until it collapses with exhaustion. Any sick or weak herd members will collapse first and the pack will close in on them.
Think open grassland with little cover.