no matter how you slice it, taking over from a captain is a tough situation. the best thing to do is to avoid the situation way in advance...when I was a copilot, my flight instruction days paid off in keeping ahead of the captains.
if you are in a difficult situation you must speak up. if no reaction say something like: captain, its now on the tape that your FO tried to get you to go around and if you **** up and kill us, everyone will sue YOUR ESTATE and take all of your things away from your family.
OR..CAPTAIN if you go around right now, I will be on your side at the inquiry...if you don't, I will move up on the seniority list when they FIRE YOUR ASS.
and if this doesn't work, push the throttles forward and keep them there...this will force the situation as things will get even WORSE and the captain will have to go around.
a cup of coffee in the face might help too.
I've only been in even one close situation...and when we landed and the captain started screaming at me I said: fine, let's go to the chief pilot and the FEDS ( FAA). I'll be able to prove you were wrong and you will lose your ticket. HE BACKED DOWN like a prarie dog after seeing the shadow of a hawk.