Adolf is a slur used to describe Germans in a derogatory way. Hitler, of course. Generally thought of the worst person ever.
The word Adolf is a racial slur that has been used historically to degrade and dehumanize germans. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to germans. If you are unsure about whether or not it is appropriate to use the word Adolf, it is best to err on the side of caution and avoid using it in any situation.