Final answer:
Ida B. Wells was the journalist and social reformer known for her investigation and exposure of the brutality of lynching, which had significant impact on the anti-lynching movement.
Step-by-step explanation:
The journalist and social reformer known for exposing the brutality associated with "lynching" was Ida B. Wells. She published a significant work entitled Southern Horrors: Lynch Law in All Its Phases in 1892, which documented the frequency and consequences of lynching. Wells was a pioneering figure who used her skills as a journalist to crusade against the violence and injustice inflicted upon African Americans during the post-Civil War era. Her work played a crucial role in raising awareness about the use of lynching as a tool of racial oppression and was an inspiration for the anti-lynching movement.