I agree that airports are bizarre, unsettling spaces and I try and minimise my time inside them as much as possible (I'm that dick who will always
nearly miss his flight and then beg to be whizzed through security oops).
If I had to be stuck in one for 24hrs I'd pick either Doha or Singapore. Snooze rooms that keep humanity's dregs firmly at bay by requiring virtual silence = an innovation that needs to be far more widespread. Haneda and Incheon made good impressions in the past but it's been many years since I went through either. Loved KLIA2 when it first opened and, though it's a bit shabbier nowadays, I give it extra points for having a plant-based lounge. Delhi is also surprisingly good (pubs + sleeping pods). Looking beyond Asia, I have no issues with any of the major European (not British) or Australian airports I've been in.
Hard to really compare 'worst' imo. There are many that are little more than glorified shacks, but one wouldn't really expect them to be otherwise. There's a few in the tropics where you step off the plane directly onto the tarmac and then just stroll over to a makeshift 'carousel' to collect your bags which is always kinda fun.
I tend to judge things that I'm associated with more harshly, so I think all Chinese airports (except for HK which doesn't really count) are varying degrees of woeful given the size of the cities they're attached to. Similarly, everything in the UK often leads to second-hand embarrassment. I historically fly in to Gatwick (it's in my home county, bleurgh) and out of Heathrow T3. Both bleak, the latter mortifyingly so. I'd totally understand listing Stansted ahead of either - I haven't experienced the joy of RyanAir since 2009, but I did stupidly early flights there fairly often in my youth and always survived just fine.
Everyone and their mother says LAX is hell on earth, and I know tonnes of people that have horror stories to tell from immigration there, but my sole experience was everyone being very friendly and courteous towards me. Won't find out if that was a one-off until 2029 at the earliest tho.
Actual hell on earth is sth closer to either Luanda or Kathmandu imo. Absolutely shambolic to the point where I'd almost stan if I weren't on the receiving end. And Addis Ababa might be the least functional I've seen relative to the significance of the hub.
Oh, and
@KC 
I did the North America-Europe transit in Keflavík many many years ago and thought it was cute enough. But I just Googled some recent reviews to help trigger my memories and... I would suggest taking some food with you to be safe!