The word that best completes the sentence is "odious" which means extremely unpleasant or repulsive.
The sentence suggests that compromise can be difficult for two different types of people - those with passionate natures and those with intellectual natures. Passionate individuals may see compromise as a surrender, meaning they may view it as giving up or abandoning their principles. Intellectual individuals may see compromise as a confusion, meaning they may view it as a loss of clarity or coherence in ideas. The word "odious" conveys the idea that compromise is repulsive or unpleasant to both types of individuals.