Worst for me was flying (think it was 876) to FRA last January. Family of 3 (adult daughter, father and grandfather) all in 18, with my boss and I sharing the aisle seats (G/J). The adult daughter was seated in F and elbowed my boss throughout the flight and sneezed on his leg (didn't use a tissue either). I have a smattering of Cantonese, and what my boss was saying about her wasn't nice
Dad was in 18K, and while he didn't didn't act gross, he did treat the FA's like serfs and was laughing like a castrated donkey at whatever he was watching on his IFE.
Grandpa was the best and, joy oh joy, he was beside me. Took off his sandals, and started cleaning his right big toe just before dinner to whet my appetite. I said "Seriously?" and was ignored. Dinner obviously didn't agree with his GI system and he was making no attempt to hide his efforts to break wind. Everyone recognizes the "One Cheek Sneak"...I sure did, since he (as Monty Python said) "F@rted in my general direction". It's very possible he may have "followed through" on one or several of his attempts to pass gas, and he decided to check this by rummaging his left hand quite thoroughly in the crack of his pants (jostling me more than a wee bit), then placing said hand on the armrest we shared.
It gets better, trust me.
As we were all trying to get to sleep, Grandpa decided that he wasn't comfortable, and decided to stretch out, attempting to do so by lifting both his feet over our shared armrest and literally trying to put them in my lap.
That did it for me. I grabbed his feet and tossed them back on his side of the armrest and said "this is my personal space, stay on your bloody side" Dad on the window then tried to scold me about being mean to his father and that his dad wasn't comfortable about flying. I replied to him that his father's disgusting behaviour was making me uncomfortable.
All of the above happened with nary a check-in by any FA, BTW.
Upon arrival in my hotel in Nurnberg about 8 hours later, I literally wanted to burn my clothes and bathe in bleach.