It isn't necessary that "this AI [have capabilities] that a human can never have".

The issue is how those capabilities (possibly shared, possibly not shared between some humans and AI) are deployed and to what ends.

There's also a speed question. Maybe AI will never be able to do things human cannot, but it seems likely that for the sorts of things most AI-excited folk are excited about, it will be faster than a human most of the time.

Humans are generally afraid of death, or have others they are fighting for; there are certainly humans that don't want power so much as they want to watch the world burn, but they seem to not intersect well with the set of humans who are adept enough to cause a lot of world-scale damage.

With an AI, it isn't clear that it will care about things the same way we care about things, or if it does care about things if those things are things we care about as well; the AI also is capable of knowing simultaneously all of the varied expertise of an army of humans.

> If no, what capabilities is this AI assumed to have that a human can never have?

If we're talking AGI, then:

- An intelligence qualitatively greater than any human or human group alive.

- A system of values that's not that of a human saint.