What qualities did Saint Sebastian have?

he had a quality of a preacher and a brave soldier

Answer

Unfortunately, the Catholic Encyclopedia says the stories recorded about St Sebastian as a soldier and brave Christian are unhistorical and not worthy of belief. While the Catholic Encyclopedia accepts that he was martyred, we can not really be sure that he even lived or died as a martyr.

Without any historical information about St Sebastian, we can not describe him or his personal qualities.