This could be translated as "You should be" or "Show yourself to be."
## a model of good works ##
"an example of doing right and proper things"
## healthy words beyond reproach ##
"teaching that does not contain any error"
## would bring shame upon someone if he tried to oppose you ##
This presents a hypothetical situation where someone opposes Titus and is himself shamed as a result. It is not expressing a current event. Your language may have a way of expressing this. (See: [[rc://en/ta/man/translate/figs-hypo]])