I would nominate Chatham. It is less than ten years old. It was built with an information office but that has closed and been leased out to some sort of land agent. It lacks much weather protection, particularly from the wind. The toilets appear to be temporary and aren't open when they are most needed. Information is abysmal, each bus stand was equipped with a departure screen which updated itself with timetabled departures without even a hint of accommodating real time information - these have nw failed and been switched off.
All in all an unwelcoming and bleak place to catch a bus.
Ahhh... I did wonder if this would come up, and very nearly nominated it myself! But then I remembered its predecessor. (Deep breath...)
The "old" bus station in the Pentagon was, if you believe the locals, a paragon of virtue. It was enclosed (by virtue of ringing the upper level of the shopping centre), so provided easy access to the shops "without getting wet". And that's about the only thing it has going for it. It was fine if you were in the "open" end, facing The Brook, where there was daylight and fresh(er) air. My bus departed from the stygian gloom of the opposite end, where daylight never penetrated, and the air was thick with diesel fumes and pigeon droppings. Oh, and my bus had the misfortune to run from next to the door to the public toilets. Which, when closed, generally revolved around the entrance being used as the toilet. 40 minutes on a winter Sunday with the odious air of stale urine, and sometimes visions of... "that was a large dog"... have clearly rendered me immune to "wet dog syndrome". As for easy access to the shops... one wonders how those complaining about the replacement ever managed the length of the high street...
The "new" Waterfront bus station is indeed not without it's own problems. The Information office is now the sales agent for the flats being built next to the bus station. The toilets used to be inside, but were moved outside after a number of, I believe the word is "dirty protests", so very not temporary. Earlier in the winter they were closed for a period after vandalism, and have now been fitted with blue lights to dissuade a certain sort of use (although not exactly prevalent, they are the only "non-secure" facilities in town). I accept it can be windy, but wind blows up the length of the bus station more often than it comes across, so there is more protection than it feels like.
The information screens are, I believe, in the process of being replaced, a previous attempt having failed to live up to expectations. They were timetable only, as there was no "old-style" real-time facility in the Medway Towns. They do tend to work when they feel like it, so it's very much "pot luck" - and not all of them at the same time! However, to describe information as abysmal is unfair - there are paper departure lists in the centre of each "platform" A & B, and at the stops in areas C and D. It's not as though there is no information at all. Often empty at the moment owing to lack of product from operators, but there is a leaflet rack just inside the door to the shopping centre, which is filled up usually weekly if there are things to put in it.
It is a very long way from perfect, but "unwelcoming and bleak" is a bit of an overstatement - certainly better than its predecessor! (Google Streetview visited on a sunny day in August 2024, should anyone wish to check)