Coby is one of the first characters to be introduced in One Piece. His introduction is from the very first arc of the series.
Coby’s main role in the series seems to be serving the role of Luffy’s counterpart. In a way, he is the same as Luffy but instead of being a Pirate, he is a Marine. Sometimes, Coby’s role in the series is seen as Garp’s role in Gol D. Roger’s era. There is some kind of special rivalry between him and Luffy that resembles the rivalry that Garp and Roger had, but despite this, there are some hindrances when it comes to this parallel. Because of this, Smoker fulfils this role much better than Coby.
The first major hindrance is very simple and very straightforward; Coby is simply too weak to be seen as the new era Garp. There is absolutely no way that he is able to stand up to, and fight even with Luffy, not even for a few seconds. What we’ve seen so far, really tells us that Luffy would absolutely wreck Coby. He could already easily overwhelm him before the Time Skip, and after training for two years non-stop, with the help of Silvers Rayleigh, I think the gap has potentially gotten even bigger. I know that Coby hasn’t been doing nothing these two years, but there is no way that he was able to catch up to Luffy in those two years.
The second thing that makes Coby’s parallel to Garp very unlikely and weak, is the fact that Coby is literally never present in the storyline to fight with Luffy or the Straw Hats. The only times that we’ve seen him was at the beginning of the story, during the post Enies Lobby arc, and during the Marineford War. The Only reason that he was able to meet and ‘fight’ Luffy was because he was summoned to the Marine HQ in order to fight against the Whitebeard Pirates. Aside from this, he has literally never shown up to fight Luffy. Whether or not this trend will continue in the future is unclear, but it certainly looks like it. These points make Coby’s role in the series a little bit vague and depending on how you look at it, you can even say that his appearance in the series overall is a bit redundant. The role of being a rival to Luffy can be appointed to Smoker, who already fulfils this role way way way better than Coby.
As stated by the guy himself in the post Enies Lobby arc, his ultimate goal is to become a marine admiral. Whether or not he will fulfil his dream and actually become an admiral is a bit hard to say, but honestly, a LOT needs to happen if Coby wants to become an admiral because we are already relatively far into the series, at the point where Luffy is going up against the Yonkou, and Coby isn’t even remotely close to Admiral-level. I’d say he isn’t even close to Smoker in terms of power and combat efficiency and Smoker has already been portrayed as being far weaker than an Admiral.
Reforming the Marines and the WG
Another possible task for Coby, is the possible reformation of the World Government and the Marines at the end of the series. We all know that the World Government is run by the Celestial Dragons, who are some completely immoral and selfish people, who put themselves above all others. It is one of the bigger plotlines in the series and they are always portrayed as the evil rulers.
It is possible and it has actually been foreshadowed quite a few times, that there will be a giant war after someone finds the ‘One Piece’, because it will likely reveal the truth about the Void Century and the foundation of the World Government. It is possible that this will trigger the rage of many people, including the Straw Hats who have been shown to be very concerned about the well-being of the people they care about, and this will ultimately lead to a final war with the World Government itself.
At the end of the War, the World Government will likely be defeated and the Celestial Dragons will likely be equalised with all the other people or even imprisoned. The World Government, including the Marines, will likely be reformed because the old leaders will either be defeated or resign after the truth has been revealed. Some people who will likely play a part in the reformation are the Revolutionary army, and some prominent new Era marines like Smoker and Coby. I think this is one of the roles that Coby will fulfil in the series, because he has been foreshadowed as a Marine who truly cares about the people and has been good at heart the entire time, unlike some other people within the marines and the World Government itself.
*Theory by S.