What is the best answer when employer company ask the question why you want to leave your present company even the brand s so good for its employee?

If you are leaving for personal reasons, then just say that.  (It is helpful, for social reasons, to say a little of the circumstances to the people you worked with, but you are not obliged to do so.)

If it is for business reasons then, as somebody on this forum put it, telling your erstwhile employer something about why you are leaving is your final duty as an employee.  This duty ceases if the employer is too aggressive or demanding.

to get a step beyond is not provocative, but on the opposite, is creative!