Monkey D. Dragon is the character who will fight Imu
I hope this isn’t too obvious of an observation. Since Enel and Doflamingo are the villains which parallel Imu the most, self-proclaimer Gods engulfing the world in a great darkness. They also have characters hat have personal vendettas against them, the ones whose main goal is to see them toppled. Wyper in Skypiea, Law and Dressrosa.
They’ll fight the respective gods and will seem victorious at first, only for it to be a fakeout. Dragon is set up to be that character for the entire story, he’ll fight Imu but will come short in the end. As always, Luffy will take on that burden and finally defeat the false God, bringing freedom to the land.
Actually Luffy and Dragon have similar goals but his dad is taking a more laid back, strategic and diplomatic approach to take the World Government down, being a Revolutionary, researching and taking action in the shadows, collaborating, team building it’s actually a very practical way to execute a plan as deadly as that, and that is why he is the most wanted man. But this isn’t going to work against Im.
And Dragon doesn’t need to die, it’s just that he will realize that his reckless son will help him in ways he had never even imagined, since Luffy will bring the World Government down.