Trinidad comes to mind pretty quickly. Congress Heights. There's a whole lot of places that beat the crap out of Petworth on the sketchiness scale.
Don’t look now but Trinidad is gentrifying too. Yea, verily, ‘n pretty fast. Capitol Hill has gotten pricey. H has turned into a happening street. The area between H and Florida/Gallaudet is hot. Trinidad is the next scootch north and it’s getting the spillover. I have two coworkers in Trinidad — 30’ish, white, female, single, and they love the neighborhood. Obviously still a work in progress, but the demographics are shifting with every sale.
The worst is Capitol Hill. In the other neighborhoods, you may get robbed, carjacked, have your wallet picked or even be killed.
On Capitol Hill they will bleed out the entire substance of your being and steal your soul.