I had a train earlier with 4 carriages. Most people chose to get in one carriage, a group of younger travellers set up camp in front of the bog door blocking it and the rest stood down the aisle looking fed up. I forced my way past, counted 40 odd seats in the rest of the train, told them all to move down the train on the PA and went and mopped up any stragglers in person. I then sent the trolley to mow down any people who had decided to remain in the way. It's a train. Camping on the vomit/rainwater/old drinks/dog poo/whatever else ridden floor is for disruption only. This seemed to work a treat.
My other least favorite people are those who try and occupy a vestibule tip up seat while I'm clearly stood in the way of it at the door panel. They get my backside and Avantix parked an inch off their nose and the odd whack in the shoulder with extreme prejudice.
Tip up seats, especially in bike spaces, should be removed - our trains that are full of standees invariably are also full of bikes as well, this leads to arguments between cyclists and seated persons about who has the right to the space, which I then have to go and resolve in the cyclist's favour.