A satisfying finale is the one all anime fans long for. Every fan literally invests everything while watching an anime series. From sleep, time, to emotions, we have everything poured in there. Your brain cells work faster than what they did during exams to come up with interesting theories that would fill in the loopholes. And at the end, where you are given all the answers, you are contented.
On the other hand, the contrary is disappointing too. In fact, the contrary can spoil more than what a good anime can give you to nurture. The best example to talk about here would be that of Darling in the FRANXX which has a lot many action sequences compiled with romance. The Franxx is made to operate successfully by making the parasites fight and this is done by pairing them up in boy or girl teams.
They are called parasites for a reason. They are short lived such that they are not even expected to reach the stages of adulthood. A group of 10 boys and girls were known to be the center of Darling in the FRANXX whose main character went by the name Hiro. He has a partner named Naomi. However, Hiro could not cope up with her and he fails to complete his combat training under such circumstances.
Due to these failure, he decides to run away from this situation and ultimately manages to find out the mysterious Zero Two who has special powers owing to the klaxosaur blood that lies within her. She has been referred to a partner killer and Hiro does know about the same. However, he gets blinded with her charm and decides to pair himself up with her to further cause immense amount of destruction.