What is most impressionable when you travel, I say bad airports, they brand the bad memories into your brain.
Let's stick with international airports, otherwise, every domestic airport in the US will be high on the list. Please limit your list to the Hall of Shame to 3-5. Give reasons and experiences why it deserved to be on the list. Have fun.
In no particular order.
Los Angeles (LAX)
This is the top of my list due largely to the worst immigration and custom experiences for any traveler, including US citizens, in the US. Why is that so, I have no idea, but, I will avoid flying thru LA at all cost. Getting from terminal to terminal is a chore, but not as bad as JFK. There are no public transportation to the airport that is convenient. You drive, call for a limo or wave a taxi, all expensive options. Once there, it's huge, spread out, just like LA, I hope you did not get off the wrong entrance. Good luck.
New York (JFK)
You better connect via the same airline, otherwise you will have to battle the archaic shuttle system at JKF, probably the worst in the world (among large hubs, worst is Sydney). Going from a terminal to another, you have to battle traffic, and the shuttle runs in one direction. Just imagine, you need to go to the terminal the shuttled jsut came from. Sit back, have a senic tour of the airport. The immigration and custom services, is probably second worst in the US.
Congestion, congestion and congestion. If you are not flying BA, you are SOOL. Trying to walk from one terminal to another, I hope you are in good shape. It's not a walk, it's a hike. The security procedures and policies at Heathrow is just too draconian. I had been trying to avoid thi sairport like a plague.
Charles de Gaul (CDG)
This is the most unorganized airport on earth. On a recent trip, I had the good fortune to fly into CDG twice. First time, arriving on an A380 on SQ, my bags came out of 2 different belts, one reserve for premium passengers (First/Business/Global Services) the the other for the rest. I am lucky to be a Global Service member, so, one piece came out as expected, but the other was no where to be seen. After a long wait, the 2nd one came out from the other belt. Oh well, they arrived. On the 2nd arrival, there were baggages from 3 different flights being sent onto the belt simultaneously. And it was not first in first out. The check in and boarding process is just as messy. Why was this not unexpected
Last but not least, Chennai (our you can fill in Mumbai or Deli).
A total mess is all I can say.