Most of the Bronx, about half of Queens, about 1/3 of Brooklyn. Manhattan is mostly gentrified these days, with only a handful of exceptions. Staten Island is odd b/c it is barely walkable to begin with, so it's neither safe nor dangerous to walk.
Everything is relative to what you're used to I guess. I'm from a Canadian suburb, where a 16 years old girl who got attacked in a dark alley at 3:30 am while alone made the news for 3 months because that was the worse thing that had happened in decades.
Now I'm in Boston, in a heavily gentrified area, and I'm scared shitless after 11 pm. People all tell me it's a super safe area, but I know a few people who got mugged a few blocks away in various occasions.
Maybe it's just bad luck. Maybe compared to other areas, a few people getting their backpack stolen is nothing. But feelings are not always rationals. I don't feel safe here.