Delta8
Regular 25min queues coming back in at passport control, the endless time it takes to check people in, the drop-off/pick-up arrangements, the quality/choice of refreshments in the business lounge(on the odd occasion I get to use it, but well behind most other places), busing to/from planes, luggage left behind, some check-in staff being able to give out 2nd stage boarding passes(eg from AMS to XXX) while others can't do it are ones that instantly spring to mind.