Those souvenir shops full of random stuff that has nothing to do with a park.
You are at a theme park, why would you want to purchase a pot plant? (Shoutout to Europa-Park)
People suddenly stopping in the middle of a path, preferably in groups and then spreading out as wide as possible.
People standing in front of the entrance, debating if they should ride or not, while allowing no one to enter the queue.
People standing in the exit, discussing how good the ride just was. I get that you’re exited, but other people might want to leave the station.
Honorable mention for the combination of 2 groups, deciding the independently from another that they need to stand next to each other at the narrowest area of a path to completely block any kind of flow and then getting angry at you for squeezing through.
Edit:
Phantasialand for going from a premium experience to a discount theme park (adult tickets starting under 30€), causing the park to be so overcrowded that I don’t even want to be there anymore. And of course for scrapping annual passes - still salty about that. I won’t spend any additional money just to stand 90 minutes in line for Taron.
Edit 2: I just realised… I apparently simply dislike people in general