Had a flight where the woman behind me kicked her shoes off and put her foot on the back of my left armrest between my seat and the wall (I had a window seat). I turned around and said “really.... do you mind” and she replied “yeah, I do mind.” Luckily it was just a quick 25 minute flight, but that’s the worst I’ve had it, other than being stuck in my economy seat on the tarmac for 4 hours, pushed back from the gate and having a 4 hour flight ahead of me.