By “deep space” I mean “not inside a black hole or underground on a rocky planet” or other types of nitpicking. Are there any supervoids that contain places that are several million light years from the nearest galaxy, and so an astronaut would not be able to see anything (other than themselves/and or spacecraft) with their naked eye? I notice that the Andromeda galaxy is more than a million LY away but is magnitude 3 and so could be even farther away and still be visible, but the supervoids can be hundreds of millions of LY across, but also aren’t completely empty.
There are in fact voids in the universe (or cosmic voids or supervoids). The voids aren’t completely free of galaxies, but there are far fewer than in the filaments so I suspect you could find a place that’s a million light years away from the nearest galaxy.
But if you don’t want to go that far, I suspect it’s pretty dark inside a dark nebula (dust cloud).
I wasn’t sure if I should include dust clouds or not, since you could be pretty alone in space and yet still inside one. I guess only objects that are at least 1 LY away should count for my question (to pick an arbitrary distance). So a dust cloud that totally surrounds a 1 LY sphere would count 
Oh, they’re much bigger than that. The Coalsack Nebula, for instance, is about 30 ly across.