For example? If user check absolutely all downloaded files on VirusTotal, as well as use the browser in https-only mode with any popular extension to protect against phishing. What else can an antivirus mitigate? Even if we look at the statistics of Malwarebytes, you can see that, for example, exploits are so rare that you can not find any in real life in your entire life.
I'm not saying that anti-viruses are not needed, since a person tends to make mistakes, he may forget to check the file security, at least, but in my opinion, guys should to choose a security solution based on the price / scenario of using the computer (games, banking, etc.) / confinguration of the computer, instead of saying that some antivirus is sufficient if you are careful. =)