Water usage is probably my biggest. Living in a high desert, my wife and MIL see no problem with filling one side of the sink with hot soapy water to wash a few dishes because “that’s just how I’ve always done it”, to watering the grass and plants for hours. All of this makes me mental.
my favorite is the ‘love to travel’ types. point out that their trips to antarctic are toxic for the environment there and they lose it on you. because cute pics with penguins are worth it!