my annual appraisal.

my superior, mentioned one of my weaknesses is not firm when I communicate to my staff.( i m manager).
i tend to agree.
How to improve on tis weakness ?

Your team abusing you because you not firm or they align with you?

If you are interested, I would suggest that you do an assessment of yourself first (root cause) and work from there to understand why and address weaknesses that could potentially cause the above.

https://bigfive-test.com/

If you need help understanding the result, hit me up.

got one or two members dont obey order. even wit my superior interference

use emotional intelligence to resolve conflict

The word you (or your superior) is looking for, is "assertive", or assertiveness.

Can help a bit, but it depends on your subordinates. A dominant personality will always know when a person is weak, and is only pretending to be strong.

U should learn about industry relation and read your company code of conduct or guideline. Did not obey order is usually under insubordination, which warrants disciplinary action. Check with your HR as well. Many managers, especially new ones, are afraid to exercise this option, hence employee see them as not firm and can do what they want.

But some manager also afraid to shoot their staff as it it could be "i help you, you help me" or it could be the manager occassionally make mistake if he shoot his staff, the staff could shoot back at the manager higher "you are manager and the one doing arrangement/planning"

Depending on what kind of order you've given. Action speaks louder than words - so check what are the actions you can take if they do not follow through with the instructions. ie. can you penalize on disobedience via appraisal which will affect their increment and bonus? Can you get HR to issue warning letter if they do not follow through time and again?

It depends on your level of authority and how stern you can be. Lenient over small matters, but be serious over bigger ones. If you appear "powerless" in a lot of circumstances, they will not respect/ follow your instruction. So don't be a pushover.

Lastly, you need to walk-the-talk yourself and follow through with your own promises or commitment.