InfernalWasTaken

My brother in christ he's literally exactly what the author intended him to be

Not really, lightning is hard counter to all 3 fruits and too fast for Sengoku to hit. In One Piece, light and lightning are the same speed so dodging light bullets isn't unbelievable. Ice melts under lightnings heat, and Magma is colder than lightning which means it has the advantage in One Piece

He is literally as fast as lightning, how would someone without future sight hit him

Give Luffy the resin fruit, it acts just like rubber does so he would still have gear 4 and all that but his gear 5 would be something else

If you want something overpowered, something like Rimurus Gluttony or Great Sage or Accelerators power. Or just do what seems like a good choice and infinite adaptation, where he becomes more resistant to things the more he's exposed to them. Maybe the ability to turn sound into light or dark which could be very good for fighting allowing him to use it like a smoke screen or a flash bang that destroys the optic nerves. You could do the ability to turn anything into a solid color or completely remove all color from an object. You could color someones eyes completely black and blind them, you could make a safe transparent and pick the lock, you could make the light infared for recon or ultra violet. Theres the possibility you could use reveal anything that is hidden, and he can use it to reveal thoughts, feelings, names, anything really. Even ways he could die. Maybe 100 Invisible Hands that can rip people and monsters limb from limb without being seen Theres Number Mans powers from worm to calculate anything including probabilities. But if you want his abilites to be shadow related then Umbrakenesis is the best choice.

Life happened, can't write anymore

Isn't the empire called the Imperial Capital?

Nah you don't need to do that, most numbers represent something personal to someone. An example is OKC KD who wore 35 for his coach who died at 35 years old. Another is DeAndre Bembry wearing 95 for his brother who was killed that was born in 1995.

Number 21 or 77

Any number from 0 to 99, can't take anyone else's number