やりとおす
やりとおす · yaritoosu · JLPT N1 · noun
to complete
やり (do) + とおす (go through) = do it all the way through: carry through to the end.
とおす means 'pierce through' or 'see through to the end', as in 通す. Put together, やりとおす is 'keep doing until it is finished'. Think of persistence that doesn't stop halfway.