The leaders of the JWS and the IBSA had their own unique inherent sins ingrained in their teachings and established doctrines.
C T Russell taught and preached Pyramidology to establish the date of Jesus's return and subsequent Armageddon. This fixated date setting carried over even when he passed on and the following leaders of the WTS propagated new dates such as 1925, 1975 etc.
It would appear the leaders of the WTS created more relevance and importance toward themselves than even Jesus and his spoken words of direction and how to be one his chosen select.
It would appear also that the leaders of the WTS/JWS were more involved in creating their own power and money through the organization that they created in their endeavor as proliferating literature charlatans.
The doctrinal mistakes that have come out of these men are many, from setting dates of Christ's return, to mistakes on blood transfusions, memorial mistakes, encouraging and influencing children to get baptized, over use of disfellowshiping , sometimes done so to protect their wrongly devised doctrines.
They sinned by removing complete sentences and words right out the bible, subjectively done so to support their own doctrines and interpretations.
What other sins can you think of and add to this list ?