We know when Kidd returns he will going for Shanks/Giants.
We know Kidd and Luffy view Shanks very differently, one sees him as an idol and the other one sees him as someone to tear down from his position.
Luffy:
From the very first chapter of one piece, we're introduced to Shanks. And you begin to realize Shanks is literally Luffy's savior, mentor and inspiration for his journey. A very important character in Luffy's life. The way he treats Shanks's hat says more than enough. In Luffy's eyes, Shanks is an idol that he admires and strives to surpass.
Kidd:
We know Kidd had a very different childhood compared to Luffy. Its abundantly clear that Kidd views Shanks very differently in comparison to how luffy does. Kidd views shanks as an enemy, as someone who he needs to tear down, while luffy views him as an idol and someone to surpass. I also have suspicions that Shanks has direct connections to the WG, and we know that is something Kidd has no respect for.
Now you might be asking wtf does shanks have to do with a fight between Luffy/Kidd. Shanks will be the catalyst for this fight.
At some point Luffy will learn about the incident that occurred with Kidd and Shanks. Either from the giants or at some point on elbaf/egghead. At some-point during elbaf, Kidd will learn about Luffy's relationship with Shanks. This will probably infuriate Kidd. I honestly would not be surprised if Kidd ends up attacking first.
LUFFY
I've explained most of it above. Their differing view of Shanks will cause them to fight. They both have undying wills. Neither one will back down from a fight..especially if its in relation to Shanks.
