My latest character went down into the ratway, and without ever being seen by any of it's denizens, pretty much wiped them out (Master difficulty). Alisse thought Gian would be tough at level one (an "alternate start" mod dumped her in Riften with nothin' but a gleam in her eye and empty pockets), but she was amazed by (and you'll never guess), https://youtu.be/A2aHmUzmxX0.

(about 30 seconds long)

I've see Gian killed the exact same way!

If you are sneaky enough, and kill the skeever seems he will sometimes think you were coming from the other direction.