This year Heraklion in Crete leads the pack.

At Heraklion Airport, like many of the Greek islands airports, travellers queue outside the airport since the terminal hasn’t got the capacity to hold everyone.Travellers also frequently report long queues; inefficient staff; filthy bathrooms; lack of air conditioning, and in general, overcrowding.
Survey respondents also noted a distinctive lack of seating, poor security, and extended wait times for both check-in and luggage.There are a few restaurants inside the Heraklion International Airport in Crete Island (Kreta), but the prices tend to be steep, given the quality.
All in all, it’s best not to let this airport experience colour an otherwise delightful Greek island, says Sleeping in Airports website.
The other three Greek airports in the worst list are: Santorini at number 2, Rhodes in 3rd place, and Chania in 7th place.
Here is the list according to the Travelers vote:
1. Heraklion International Airport, Greece (HER)
2. Santorini National Airport, Greece (JTR)
3. Rhodes International Airport, Greece (RHO)
4. Paris Beauvais–Tillé, France (BVA)
5. London Luton Airport, United Kingdom (LTN)
6. Rome Ciampino International Airport, Italy (CIA)
7. Chania International Airport, Greece (CHQ)
8. Cluj International Airport, Romania (CLJ)
9. Berlin Schönefeld Airport, Germany (SXF)
10. Berlin Tegel Airport, Germany (TXL)