osadia y mas...
what would be the best translation for "...pues aguantar a semejante viejo mañoso debe ser toda una osadía."
the context was a friend congratulating his friend on his wedding engagement, this specific part being geared toward the future wife...i think your translation were actually quite good. the phrase is obviously sarcastic.
The subject of the phrase is aguantar, so it doesn't really make sense to me to say that the act of aguantar is una osadía. However, my GUESS as to the intended meaning is something like this:
...putting up with a stubborn old fool like that must be a real pain...
...you have to be brave to put up with a stubborn old fool like that...
More context might help.
i was really looking for a good translation of the whole phrase
Have you tried the dictionary? Try boldness or audacity .