One Piece Volume 39 : Scramble

Vol 39 cover the Sea train Sub arc and the start of the Enies Lobby arc with the Crew just arriving on the aforementioned Island

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Inhuman

Frank Fight Nero a Four Powers Master , A person who as only learned 4 / 6 of the " 6 Powers Technique " where Franky with great effort eventually defeats him making them high relative

Lucci after learning of Nero's existence and that he only has 4 of the 6 power decides he does deserve to be part of CP9 and kills him saying " You're only Superhuman... if you have the entire six powers repertoire down" putting Nero , Frank , Luffy , and Zoro at a Sub or pseudo Superhuman level

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Power Up ?

Zoro Fight a Marine Captain but the important part is the Zoro Manifests an Aura which we Learn in the upcoming volumes is part of the power up he get but here it show that they are increasing in strength on their way to Enies Lobby explaining their seemingly out of no ware Power ups

Sanji after fighting his way through the Sea train with a fight will a name opponent that parallels Franky's fight than arrive at the front of the train and attacks Blueno not being able to harm his iron body with a base attack but with a named attack almost breaking through , something a named attack from Luffy couldn't do which indicates two thing , Sanji is getting stronger as well , and at some point Sanji caught up with Luffy and Zoro and in a tiny way in this moment surpassed them

Luffy States " I'm Gonna Go Send everything and everyone flying!!! I've got a move I wanna try out too " which said move we lean later is a power up and even know Luffy doesn't engage in any fights on the Sea train he is going to fight thousands of unnamed fodder which give him time and pressure to grow as well

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Power Scaling Recap