1 – “Surgeon of Death” Law
Undoubtedly the best Surgeon in the World; with the power of the Ope Ope no Mi, there’s no surgery he cannot complete. Hell, he can even make people immortal at the cost of his own life. He saved Luffy’s life after Marineford and his fruit is generally regarded as one of the most valuable in the world because of it’s astonishing capabilities.
2 – Crocus
The Pirate King’s Doctor. We don’t know much about Crocus’ doctoring abilities other than that he was so great in the medical field that the Roger Pirates sought him out for his skills and he was able to hold back Roger’s incurable disease for as long as he possibly could have and that he was treating Labooon.
3 – Dr. Kureha
When it comes to pure experience, Dr. Kureha has got everyone else in the world beat. With her 100+ years of medical experience, she could easily cure what others thought to be incurable. She taught Chopper everything he knows about doctoring and honestly, I think she still beats post-timeskip Chopper out when it comes to the medical field.
4 – Chopper
He was taught by Dr. Kureha herself and he’s the doctor of Monkey D. Luffy – Future Pirate King. His dream is to one day become the greatest doctor in the world, capable of curing any disease, but for now i’m putting him in 4th. Post timeskip i’d say he’s rivaling Dr. Kureha in skill, but I honestly can’t see him being above her with the insane amount of experience she has.
5 – Dr. Hogback
A renowned doctor around the world. He was skilled enough to be recruited by 320,000,000 million belli man – Gekko Moriah. Over his years working with Moriah, he reanimated hundreds of corpses and even worked to fix the body of the continent puller Oars. Pre-timeskip he might be above Chopper but honestly I think Chopper has surpassed him after his timeskip training.