I would have to say external only.
Oh, c’mon, did Superman, or Clark Kent, ever call in sick?
Flying! I’m kind of shocked that anyone would choose differently–it seems so obvious to me!
I wouold say “perfect health” is a different power. Add it to the list.
I disagree. He had perfect health because his body couldn’t get attacked by diseases. Or anything else. He inhales poisonous gases, he eats toxic and explosive substances (I believe he has eaten plutonium in the past.) The only thing that has caused him problems was when someone managed to get krytonite particles injected into his bloodstream.
Presumably there might be some – er, Kryptonic, Kryptonese? – microorganisms that could do some damage, but our puny human diseases…
Kryptonian, and yes, he could get kryptonian diseases, if any still exist. But they were a super-scientific civilization for hundreds if not thousands of years. They may have eradicated all diseases on the planet, or used genetic manipulation to make their immune systems able to handle anything the encountered. We may find out now that Kandor has shown up on Earth with 100,000 more super-powered Kryptonians.
Flying! I have flying dreams all the time.
invulnerability