Ronald: Did you hear about Jacob?
Heejin: Our old friend Jacob? What about him?
Ronald: He made a killing in the stock market last quarter.
Heejin: Really? I should get in touch with him for advice. I lost a lot of money last quarter.
Hugh: I can't go to your party tonight. I have to work - and I'll probably make a killing serving drinks.
Jaime: No kidding. At the bar?
Hugh: Yeah, last week I made $200 in two hours!
Meaning: to make a lot of money or be financially successful. The verb "make" in this idiom must change to agree with the subject.