Maryland. Sprawling, unstaffed, ungated, hovers somewhere between undermaintained and filthy, and in the middle of the roughest part of Stratford. Surprised nobody else has mentioned it!
Mill Hill Broadway. Brick bunkers abutting a motorway. No life, just the din of cars (Hendon has this to an extent, but the environment is a bit nicer)
Bruce Grove, White Hart Lane, Silver Street, Southbury - neglected by several successive operators, understaffed, in pretty hairy areas.. I think I can look after myself but if I have a 15 minute wait at one of these of a late evening I'll consider a bus to get me home. They're just unpleasant places to be.
Ponders End is grim - not dangerous, but often quite bleak with the lack of life and the traffic roaring past on the parallel road. The 25 storey tower blocks looming over give a forbidding air too (they're being decanted for demolition in the next few years).