Adolf Hitler was the leader of the Nazis and is referred to as the most hated person in all of history.
It is unknown that Adolf Hitler was a Cahill, referencing the fact that in 'The Maze of Bones,' Lucian Natalie Kabra mentioned to Alistair Oh that there was a war between the Ekaterinas and Lucians and that "It didn't go very well for your branch (Ekaterina), now did it? " However, these people forget in the next sentence Alistair mentions a 1908 explosion in Siberia (Lucian work), and that Adolf Hitler was seventeen at the time.
The Führer may have been a Vesper. During the Holocaust, every corpse was stripped of its valuable items... watches, rings, etc. It is not clear what branch Adolf Hitler was in. He could be a Lucian, or a Vesper. He and his wife committed suicide at age 56 because they knew that they were about to be captured by the Soviet Force.
According to The Cahill Files: Operation Trinity, Adolf Hitler was not a Vesper nor a Cahill. The Vespers persuaded him to steal the altarpiece which Hitler also wanted as he believed that it lead to a treasure that gave unlimited power. That is why the Vespers easily convinced him to steal it from the Louvre.