Paris -- Charles de Gaulle Airport
CDG got the "worst airport" award two years running from
SleepingInAirports.net, but this year site owner Donna McSherry decided to give it a break, in part because now "the homeless population was being segregated" to "the Third World inspired Terminal 3." Big takeaway here: If you're worrying about how to distribute your homeless population, you're one of the worst major airports.
De Gaulle is a huge airport where many people have to transfer, but it's an awful airport to change planes in; many flights require a change between CDG's various scattered terminal buildings, which are connected primarily by slow, confusing shuttle buses. Changing planes here is tiring, irritating, and sometimes a little terrifying.
This being Paris, there is also usually a strike on.