Funny thing about Kizaru and his devil fruit is that he is limited due to his human body.
While true that his devil fruit is light and light speed is beyond human capacity.. Their are some penalties to this...
1) Light at it's fastest has no mass meaning it can't do any damage whatsoever so kizaru moving that fast to harm someone is impossible has 0 mass = no damage
2) The beams that Kizaru shoots aren't in essence just light.. It's simply energized and powered up protons light which has energy + mass and thus loses it's speed. Perfect example is a laser which is light but charged up and more powerful.
3) When Kizaru says kicked at the speed of light.. What he is essentially saying is that his kick is not moving at the speed of light. Its that the impact is accelerated at the speed of light which since light has 0 mass once your mass is calculated in the target will be moving much much slower although still going pretty fast to be hurt. It's sort of like a railgun however your mass will determine velocity
Hope that clarifys some things
While true that his devil fruit is light and light speed is beyond human capacity.. Their are some penalties to this...
1) Light at it's fastest has no mass meaning it can't do any damage whatsoever so kizaru moving that fast to harm someone is impossible has 0 mass = no damage
2) The beams that Kizaru shoots aren't in essence just light.. It's simply energized and powered up protons light which has energy + mass and thus loses it's speed. Perfect example is a laser which is light but charged up and more powerful.
3) When Kizaru says kicked at the speed of light.. What he is essentially saying is that his kick is not moving at the speed of light. Its that the impact is accelerated at the speed of light which since light has 0 mass once your mass is calculated in the target will be moving much much slower although still going pretty fast to be hurt. It's sort of like a railgun however your mass will determine velocity
Hope that clarifys some things