The length of time it goes on. When I'm in charge of the world and everything in it, it will be an offence to display anything christmassy in public before Dec 4th, and any decorations will have to be removed by midnight on Jan 2nd.
Cheesy Christmas music being played every-fucking-where. A few years ago I abandoned a trolley full of shopping in a supermarket and walked out when I heard Aled Fucking Jones walking in the fucking air for about the 95th time in 3 days. It could just as easily been Slade or any one of a few dozen god-awful Christmas singles.
The crowds.
The waste.
The screaming, over excited, grabby children.
Having to go to some shitty chain pub for a Christmas meal with DP's whole extended family. It's MILs "treat" for us all, the food's always crap, it's a fucking rip-off and I dread it more with every year. I've managed to get "a nasty cold" a few times and genuinely had flu one year, but I can't get a sick note every year. Tbh, flu is preferable to going for the bloody meal. I love MIL to bits, but really don't need this.
Going out to a chain restaurant for a shitty meal with work. We all really get on well, and enjoy each other's company, but I'd far rather just go to a pub and have a natter. Preferably around May or June, when it's nice enough to sit outside.
This year, we're home alone again and the engineer man can't fix my main oven, we're having lasagne for Xmas day lunch (proper, made entirely from scratch by DP). I love a traditional Christmas lunch, but I'm quite looking forward to not having to peel anything or make pigs in blankets.