One of the most important events in the One Piece world was the dissolution of the Shichibukai system. The seeds for this were planted long before the time skip of the series when Sir Crocodile, one of the former Warlords, tried to run Arabasta into the ground. Thanks to Luffy, the country was saved, however, and the threat that the Shichibukai posed to some countries was made apparent. After the time skip, Dressrosa faced a similar situation with Doflamingo, however, in his case, the country had already suffered for over 10 years.
Admiral Fujitora made it known that his dream was for the Shichibukai system to be completely abolished. At the Reverie, this idea was put forward and with an overwhelming majority of leaders supporting this proposition, all the Warlords were stripped of their position. Shortly afterwards in One Piece 956, fans saw the aftermath of the abolition of this system. Koby, in particular, was seen on his way to Amazon Lily. According to him, he was on the way to capture the Pirate Empress, Boa Hancock. The question remains, however, does Koby have what it takes to defeat Hancock?
Hancock's Strength
Hancock is an incredibly powerful pirate and this is something that even characters such as Sengoku acknowledge. Just after one voyage as the captain of the Kuja Pirates, she was given the title of Shichibukai and an 80 million berry bounty was slapped on her head, which just goes to show that she is a very rare class of pirate. Being a warrior from Amazon Lily, Hancock is an incredible user of Haki. Her sisters, Marigold and Sandersonia are both users of certain advanced Haki forms, such as Ryuo.
Hancock herself commands the Color of the Supreme King as well and it wouldn't be a surprise at all for her to be able to coat herself in this power, especially since the Kuja are the only tribe in One Piece known to have a mastery of Haki. Hancock, being the strongest of the tribe by far, most certainly knows how to make use of this ability. That's certainly not all that she offers, however. Hancock is also the user of the Mero Mero no Mi. Using this power, he can turn anyone who lusts after her into stone, along with turning anyone and anything into stone on physical contact regardless of their attraction to her. Evidently, Hancock is one of the most powerful characters in the entire story.
Koby's Strength
Koby, on the other hand, is not all that powerful just yet. He dreams of becoming an Admiral of the Navy, however, as of now, holds the rank of just a Marine Captain, which is the same position that Smoker held before the timeskip of One Piece. Koby is also a member of the secret Marine unit called SWORD. However, even there, he places under X Drake in terms of authority and power. Given that Drake was nothing special during the Onigashima war, fans can imagine how strong Koby is currently. He certainly has a lot of potential, as evident from the fact that he will one day become an Admiral of the Navy. However, for him, defeating Hancock currently is not plausible.
Koby's Ideals
Another important aspect to notice here is Koby's ideals as a Marine. Oda has carefully planted seeds for the corruption of the Navy to be revealed slowly in the story. Koby is a person who always wants to fight for what is truly just. During the Marineford war, Koby was attempting to save pirate lives despite being a Marine, as the violence, according to him, was excessive on the Navy's part. Furthermore, Koby was mentored by none other than Garp himself, and he would certainly have informed the young Navy about the corruption in the ranks of the organization.
As such, Koby would know better than to attack a whole island of innocent people and former slaves. Furthermore, Kobe idolizes Luffy and this is no secret. Even Rebecca, Shirahoshi, and Vivi were able to tell this during the Reverie arc. Hancock is also a huge admirer of Luffy, going as far as to develop feelings for him. The two could potentially strike a partnership together in some way or form.
The Likely Outcome
If Koby and Hancock do fight, it will likely end in the defeat of the former as he is certainly not up to the level of the Pirate Empress. Provided that Koby has support with him in the form of the SSG, he can take on Hancock and capture her. However, given that Kobe isn't a Government dog, fans should expect him to find a solution to the problem by following his own model code.
Surely, Koby will not take a former slave back to slavery. At the same time, he cannot attack an island of several thousand innocent people simply because they are a part of the Kuja. Interestingly, fans know that the secret marine organization, known as SWORD is working behind the scenes, possibly against the CP0, who act as the SHIELD. As Such, an understanding between the Kuja and the SWORD of the Navy might also be possible.