Relativity of Intentions

The topic of relativity of intentions popped up while we were talking about Kant during our class lectures, and it peaked my interest. 

Take Hitler for example. He believed whole-heartedly that he was going to save the world during World War II. As another example, heroes. Heroes intentionally set out to do good- such as the firefighters and police officers rescuing people from the buildings during 9/11, yet the consequences were bad (death). 

This causes me to think that we as humans always think that we have good intentions when setting out to do something. 

This leads me to question do all good intentions lead to horrific consequences?