Jovami6729
You might be overstating the threat Iida represents. First, remember how Hulk best Juggernaut during the World War Hulk series. Iida has similar weaknesses. Second, for all that OfA can stockpile, not only does Yami have his own OfA now, but darkness is infinite. He can literally keep absorbing OfA's energy output from Iida and exhaust Iida that way. Third, just as OfA becomes stronger against enemies over time, it also takes a greater toll on the user's body. The hands down easiest way to deal with the OfA mess is for Iida to try to go full power and end up blowing himself up, killing him before he has a chance to pass it on. And fourth, given how One Piece DFs can have abstract applications, so too can Yami's power. This means that not only can he absorb damage, he can also absorb memories, will, etc. Perhaps even the soul. Leave Iida (and OfA) an empty husk, and his threat is neutralized no matter how powerful OfA is. A car can't start without any driver, after all.