I was unfortunate enough to be sat next to 2 very drunk russians on a 6 hour flight to Oman (we were going to Sri Lanka) a few years ago.
The staff initially refused them any more drink, but because of the abuse they were getting, eventually continued to sell them drink, despite our protests. They soiled (puked), and then destroyed the seats, they abused everyone around them, we moved away from them when we could, but there weren't any empty seats and they continued to abuse the staff, despite the fact they still served them. I felt so sorry for the staff who had to deal with it, they tried, but it threatened to get violent several times.
Worst flight I've ever been on anywhere.