The biggest mistake I have seen in PMI is the individualized approach to integration. Operations in one silo, IT in another, HR, Commercial and so on. When each group is tasked to “integrate” then each group will push their own agenda often with the gross assumption that the rest of the business units will fall in line. It is through this fragmented approach that you get many duplicate, parallel, or succinctly different processes happing all at the same time, requiring additional resources to manage what should have been more efficient.