Things that I hate
1. People disrespecting others for their religion, their preference in a mate, or their identity
2. People thinking they have the right to tell you to stop doing something that is legal to do just because they are butthurt about it.
3. When I get a papercut while reading a signed copy of a good book and I get blood on the page.
4. When a 3d print is at 20+ hours in and fails.