Maybe I blocked it out before i even arrived in Berlin, but I have never felt uncomfortable, worried, or scared while at Kottbusser Tor. I suppose this is because most of my time spent here is transferring inside between the U1 and the U8 and not dealing with loitering folk outside. Yeah the junkies hang out outside and if you walk under the tracks you might get shit on by pigeons, but it's not altogether terrible. And if you are outside, keep your wits about you and you'll be OK.
For me, actually, the worst part is the mob of people who clog the escalators instead of adhering to, what I am relatively certain, is the universal stand on the right, pass on the left, rule of escalator usage. But if you don't have a quick transfer to make, looking at the faces of all the people going the opposite way is always an interesting way to pass the time. Also, reading the graffiti on the U8 walls can be entertaining.
There's also the issue of the escalators themselves being totally on the wrong sides, but I won't even attempt to understand what the person who designed it that way was thinking. read more