Well the first arc doesn’t has a final boss, the second arc didn’t end with an epic fight against Kurolo, only greed island had a boss battle which is why it’s my favorite arc in hunter x hunter and finally Chimera ant arc had Meruem but he never interacted with the main characters and they were not involved in a fight against him. Also the power system in Hunter makes it so difficult for epic match ups to accur it’s very confusing and details can be forgotten easily and there’s a clear limit to characters that they can never overcome no matter how much they train
First arc has the Hisoka stealing card situation and tournament where Gon had his arm broken. But yeah not really a Boss.
Phantom Troupe Arc does had a Boss Battle. Kurapika and strong guy I forgot name.
Power System is complicate sometimes but other times are way easier to understand.
Gon and Killua has easy abilities to understand. Kurapika is more difficult.
What we learn by Gon and Killua that you can get stronger with Nen by training to increase and training to control better. By Gon and Kurapika we also learn there are ways to boost your Nen and overcome your limits.