Ohh, list can go on. I'll just name some, but I could think of 100.
1. The Spammers.
2. Greifers. Like, greifing is still a thing? ;/
3. The 10 year old rager. Just accept I can go 10-0 in PVP.
4. When people think pranking means blowing your whole house.
5. People never make it to planned events, like UHCs, "stating they have a life," but was really playing CSGO.
6. Anyone who ever dares to type in chat, "Kevin Durant > Russell Westbrook."
7. People who think they know everything.
8. Like you said; people who build big structures in the middle of spawn and its just a big square wood building..
#8 made me flip my lid. That exact thing happened with a guy on my SMP. I've known him for awhile, and I thought he was beginning to become a decent builder. But boy was I wrong... he erected a wood shop RIGHT next to the center spawn hub. There is glass and stuff so in the hub you could just see his eye sore of a shop. Anyway... it was literally a big square wood box -- he thought that adding spruce logs on the corners (at the same depth level as the dark oak planks he built his box out of) added texture and depth... well needless to say, he hasn't played in awhile and apparently doesn't plan on playing anymore. So first thing I did was tear down that terrible building, and I was happy about it.