So many wrong answers to a question with such an obvious fucking answer.
Kidd is Luffy’s rival. Blackbeard is his arch nemesis. Move on. Their relationship dynamic, their parallels, and the fact that they have the same ambition all put together makes it very obvious. Characters in the show have already called Luffy and Kidd rivals. Queen even says to Luffy in Udon something like, “Why do you want to save him? Is it because you’re rivals battling it out in the same generation?”