Hunter Exam - Showing that this wouldn't be a series where greater strength overcoming someone was law, as well as setting up its differentiation from the standard Shonen in a few ways (eg. the tournament formula being flipped on its head).
Zoldyck Family - Fleshed out the Zoldyck family somewhat well.
Heaven's Arena - Established Nen as a complex and interesting power system, as well as the structure of Heaven's Arena allowing for a tournament-esque scenario where a protagonist's victory wasn't assured.
Yorknew - Good characterisation amongst all of the Phantom Troupe and kept the tension high with how outmatched the main cast were and how circumstantial Kurapika's use of his contract would need to be to take down the troupe.
Greed Island - Well fleshed out training routine for the advancement of Nen.
Chimera Ant - Great theme exploration on human nature, excellent character development for Meruem, many other fleshed out and developed characters such as Shoot, Knov, Shaiapouf, etc. Good use of strategy and tension and some nice narrative parallels between many characters.
Election - Killua's arc was decent until he left Gon to go with Alluka.
Dark Continent/Succession War - It at least has less asspulls than the Election Arc
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In all seriousness though, the direction taken for Kurapika's character in this arc is OK. Seeing Hisoka take down the troupe one member at a time is good too.