Managing Your Manager: Dealing with a Bully

Get involved early. 
Pay close attention to signs that your normally mild-mannered boss may be turning into a bully. If you suspect your boss is bullying you under stress, it's best to reduce the stress. Have you had a bad day? Do not attend unnecessary meetings until you feel the coast is clear. Did he get pushed around by his boss or by a client? If you are unsure, move away from the situation. You should not be near a snarling animal's nose, and you should also avoid a manic bully's path until things calm down.

Set limits.
Do not be a martyr, work excessive hours, or tolerate rude behaviour. You will not do any good for your company or yourself. On the other hand, saying no can be liberating and may even help you earn respect from your boss.
Talk to your coworkers. Does your boss bully you only, or does he bully all employees? Is it because you aren't doing your job well or something more personal? Your boss may not like you. Teach suggests asking your coworkers for their advice.

Give positive reinforcement.
 Tell your boss how you feel inspired by her positive attitude and politeness. To send the message, you can go overboard if necessary. "Never respond to bullying by fighting fire with fire.

Be a role model.
 It can be helpful to set a good example for your boss. Praising others' work, giving credit, and being calm when your boss isn't will help you see the light.

Talk to your Human Resources department. 
If all else fails, Teach says to your HR department. Remember that even though they may listen, this doesn't mean they will act or be supportive of your cause. HR might overlook bullying tactics if your boss is successful. One example, I have seen many people leaving a department due to bullying supervisors until the supervisor was fired. Is HR responsible for this mass exodus of employees? "I believe HR departments should be more proactive in preventing workplace bullying. "

Sources:

https://www.indeed.com/career-advice/career-development/workplace-bully

https://www.psychologytoday.com/us/blog/cutting-edge-leadership/201201/how-deal-difficult-or-bullying-boss

https://www.entrepreneur.com/article/320696