Was asked to comment here, but I'll clear one thing up. D not only has Layered Regen but also Layered Hax and Resistances. As others have pointed out in this thread, his Reactive Evolution is OP and basically lets him resist and be unaffected by shit that affected him previously.
Reading through the comments, I'll address the stuffs raised against D :
- Power Null is not doing jack as D naturally resistant to that due to AR's effects. Moreover, his Reactive Evolution takes care of any layered hax that are potent enough to bypasses his resistances. Such an example is D fighting Lord Rocambole who nullified D's aura as soon as it touched the latter but later on couldn't nullify D's powers. In the same fight, Rocambole could initially Copy D's moves but later on couldn't mimic him.
- Curse and Resistance Negation aren't anything new in VHD. D already resists AR which can negate resistances but D resisted that. Curses D has layers of Resistance to that too via his Reactive Evolution.
- D already eternally stalemates his Dad who has the same powers as D plus more including all the Vampires powers. So any form of Incap or Non-Physical hax are completely out of question here as D resists everything he and his Dad has but on a higher scale.
- Layered mind hax, power null, concept hax, reality warping, etc are moot here since D resists all of that too. On top of that D literally doesn't need his Conceptual source of energy because his source of power comes from the Void aka Sacred Ancestor.
Even assuming that somehow Yakagi manages to hax D, how is that exactly killing D? I don't see anything to suggest Yakagi could bypass NEP or High Godly Regen. Incap itself is out of question because the moment D is affected by a Hax, he will adapt and evolve to become resistant to it as he did in most of his novels.
As for D taking on Yakagi, he'll eventually evolve to one shot Yakagi since D has outright shown to evolve and cut down beings he couldn't cut before. In addition, he also has his dad's abilities which can bypass layered resistances such as Death Hax, Immortality Negation, Fate Hax, etc. He can also copy Yakagi's powers, use miracle bloodlight to bypass Yakagi's resistances including his Resistance to Resistance Negation, Etc.
EDIT: Also, D with AR would mean Yakagi's entire arsenal is getting copied the moment the match starts while D will simply negate his blessing and rewrite his fate.