He's without a shred of doubt the best written character imo
From a clueless little boy who lost his parents, to a priest living a somewhat normal life, then his work as a revolutionary eager to take down the WG, raising his tragic friend's daughter, then being branded as a tyrant and forced to join the Warlord roster, and being forced to become a human machine that ruthlessly obeys the commands of those who detests most so he can save the one he loves most, only to end up as a complete machine devoid of consciousness all while being cloned to become the new face of weapons of mass destruction.
His story is literally the embodiment of the World Government's 800 years of tyranny.
It is so tyrannical and cruel that a saint like Kuma was bent and twisted terribly enough that he ended up having no remorse about killing his best friend's son. It was only because Zoro's determination and sacrifice were so great that he allowed Luffy to live.