That guy was big-headed, he thought he was the smartest person in the world.
I don't want to sound big-headed, but I thought my picture was the best.
down-to-earth: someone who is practical and close to reality, who accepts other people as equals 实际的;脚踏实地;现实的
Despite his wealth, he was a down-to-earth man.
Gloria is probably the most down to earth person I've ever met.
slave driver: someone who makes other people work really hard 逼迫他人拼命干活儿的人；苛刻的上司
My boss is such a slave driver. I had to work two weekends in a row.
He was a very kind person but could be a slave driver.
have a short fuse: someone who has a tendency to get angry quickly/easily 脾气暴躁的，易怒的
fuse /fjuːz/ 保险丝，熔丝；导火线，引信
I don't think he should become a teacher, he has such a short fuse.
The boss is known to have a short fuse.
I'm usually a pretty calm person, but whenever I start driving I find I have such a short fuse.
