What will happen if a refugee boarded a plane, but that plane is diverted to the place where he is persecuted? [closed]

It is possible that he will be persecuted.

There were few of such cases (usually just for very important reasons, and few of the worst criminals/terrorists).

Often airlines will cooperate, or they will risk to lose permission to fly above or into that country.

In any case, this has a lot to do with diplomacy, so it is difficult to have a definitive answer. As diplomacy rules, it depends on relation between the many countries (passenger, diverted state, airline, plane), consequences, etc. But if a country do it to capture a passenger, the diplomatic decision (also unilateral) have already been taken.

If diversion was not intentional (for such reason), and they discover later the passenger name, this case would be more complex. Probably the country will try to delay the new departure, waiting to get a sort of permission from other countries, or just to decide that the diplomatic risk is worth.

But this question has much more to do with politics and diplomacy, and not much about law and travel.

And in your hypothetical case: When you flight to Taiwan from Europe, one usually flight above mainland China, so China has power to divert the plane for security reasons. There is very little one could complain. If he want to be safe, he should flight to Japan (Siberian route) and back, or via India and Philippines (or nearby countries).