While this may not be the most disgusting thing in this thread, it's something that still haunts my dreams.
A couple months ago on an EK flight DXB - CAN in Y, I was in an aisle seat sitting next to a heavily rotund Asian guy. When I say big, I mean I literally was only able to use slightly more than half of my seat as his rolls were pouring over the arm rest. Being an extremely overbooked flight, there was not a single other seat available. He proceeded to constantly munch on the most obnoxiously repugnant snacks and drank a quarter of his weight in beer (He would ask for two at a time). As such, he would constantly let loose some really dank anal emissions. However this isn't the most disgusting part.. what got my goat was that a little while after I eventually dozed off, he attempted to get up and visit the restroom. BY SQUEEZING BY ME. I woke up with my face pressed against his acrid posterior.
I stood by the galley for the rest of the flight chatting with the FAs. A couple said they saw how uncomfortable I looked and they felt really sorry for me. Ever since then I've only travelled in J to Guangzhou.