1. They send mixed signals. They act like your best friend one minute, and yell at you for something really minor the next. Another example is acting like deadlines aren't a huge deal, but they get mad if you miss one.
2. They don't give you any GOOD feedback. Meaning they only tell you when you did something wrong. If you never get any compliments from them, it kills your motivation.
3. They never meet with you one-on-one, except for your annual review. They should be having regular meetings with you, and not just to give you a lecture. They should ask questions, and actually WANT your input because they know it's valuable.
4. They play favorites. One example is letting certain people get away with things, like showing up late. But if other people do it, they get in trouble.
5. They make it crystal clear that you work for THEM. A good boss makes you feel like you're all working together. They don't just bark orders, or feel the need to remind you that they're the boss.
(Business Insider)