Blockbuster is a slur used to describe Blacks in a derogatory way. A real estate agent who sells a home in an upper-class white neighborhood to a black family, thus lowering the values of other homes in the neighborhood. (This can be stretched to include inviting a black or minority friend over for dinner.)
The word Blockbuster is a racial slur that has been used historically to degrade and dehumanize blacks. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to blacks. If you are unsure about whether or not it is appropriate to use the word Blockbuster, it is best to err on the side of caution and avoid using it in any situation.