I’ve had several bad bosses. What made them bad was their fundamental misunderstanding about what work is: an exchange of labor for money. Knowingly or not, they each thought being my boss meant that they could ditch normal, healthy adult human boundaries. E.g.

• Treating me like a child. Being younger, less experienced, or a different gender/race/etc is no excuse for condescension.
• Expecting emotional labor for their personal benefit. Don’t look to your employees to make you feel good about yourself. You might think, “But Brad loves going to lunch with me, we’re buddies” but Brad is thinking “Fuck, fake a smile and go with it so my job isn’t in jeopardy.”
• Treating me like an appliance instead of a human being with needs outside of work. Sometimes those needs come first. Like the need to take a sick day. Don’t penalize employees for that or demand that they prove it to you somehow. Again, they’re adults. If they say they’re sick, grieving, whatever, believe it and move on.
• Asking me if I like them as a person. Just….no.
• Not respecting my time off. When I’m off, I’m off. Let your employees forget you exist. That “one more thing,” or “I almost forgot,” builds resentment. Like my boss sent me a long ass text on New Years morning and was perplexed as to why I was unable to engage in a conversation with her. Fuck off sometimes. They’ll love you for it.
• Expecting me to make them look good. Employees are there to support the work. Not advance your career or make your life easier. Think twice about your motives when asking them to go above and beyond.
• Upholding archaic, unhealthy norms like butts in seats by 8 am or else when the job doesn’t require rigid punctuality. I commute 65+ miles to work so I can arrive up to 45 minutes late, depending on traffic. My current boss doesn’t care as long as the work is done and I love her for that.