Many people tend to underrate the alleged implications of the Gamma Knife effects and not merely general performance wise but they forget that health has been associated with CoO in the manga. Whitebeard had such bad CoO due his health condition, I don't think just because of his old age at all and age is also an health indicator anyway. Perhaps even CoA.
Gamma Knife is no Joke
Being hit by it is a Major Nerf/Injury to almost any Character, even Yonko such as Shanks & WB
Only Kaido & BM can Tank it due to their Skins (+ Cyborgs ofc such as Kuma)
Anyone who have Normal Human Skin/Body will have trouble fighting after being hit by it