@RamistaR:
That's 100% interpretation bro. I agree for Kizaru not using haki but not for the same reason. He was bored and found a pirate, no need to use haki when you are just enjoying yourself. Then he saw Hawkins transformed and assumed that it was a parameccia, still no need to use haki there.
By the way it's also 100% interpretation but I think haki doesn't work on Hawkins, I have a good and a bad reason to think so.
First, haki allows you to hit a devil fruit user, but does not negate ability. His devil fruit doesn't prevent people to hit him in the first place. It only tranfers the damages to someone else.
Second, he would be an easy target if haki was enough.
As for Vergo vs Law, I think Law did use haki. We know nothing about Law's fruit. You assume that it allows him to cut things more easily. Well I think he cuts things and people with his own talent of swordman. For me the devil fruit only allows people to survive the injuries. So he needed haki to cut Vergo in my opinion.
Well after his kick did no damage and some dolls fallen of Hawkings you dont need to be an Einstain or genious in fighting to figure out that Paramecia DF protected him from damage so presumably Kizaru was really playing with Hawkings as you said. Though I still dont think that attacks like fire or light or Laws slashes with sword can be really imbued with haki.
What would haki add to fire for example? Or to Kizarus laser? It would not make fire harder or laser hotter I think so beside no use, those things itself are form of an energy and not objects and CoA for all that was said can be imbued to physicall stuff.
Sure Haki doesnt negate ability but it makes it possible to damage DF user- if it can damage logias why not paramecia? Luffy was hit to the face with CoA lately and it gotten him allright- Doflamingo knew he is paramecia and still he went for haki punch so your argument doesnt hold ground in this case imo.
If Law used haki then how it is that Vergo was alive after slash?
All Law did was overpowering Vergos haki with his DF ability. Normal kind of slash with haki would kill Vergo. Haki is making physical damage to DF users ignoring their DF powers and all other people, so why there was 0 blood if Law used haki to strengthen his attack? Zoro imbued little slash to the face he did to Monet and blood flown out of the wound instantly. Haki is destructive ability while Law power was shown to be non lethal in all cases.
Beside I see Laws ability as not ability to make people being able to survive injuries- his slashes are non lethal all the times in his room, sure but people outside of room have same injuries yet still live so its not that Laws ability is saving them from dying, Laws ability cuts them to pieces and makes it possible for those pieces not to die out so to say even after stopping usage of ability. For me only ability till now that Law used with Haki is his scalpel against Doflamingo. Why? Because it was the Laws exact same move he used against Smoker, when he used it against Smoker there was no blood.
So why it was possible for Law to imbue his DF power with haki in this case? Because it was attack that makes use out of physical part of Laws body- his hand. So his Scalpel is cutting but its also non lethal as we seen against Smoker, if used with haki it slices and wounds Laws enemy- as shown by Doflamingo.
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If Law would have used haki against Smoker he would bleed same as Monet did against Zoro or like Doflamingos face was bleeding later on.
COA haki is the only explanation of him being able to form a solid light sword, that means he coated his light shaped sword with COA to make it solid.(my opinion.)