Who was most famous for having a negative effect on the Civil Rights Movement?
If by "negative effect" you mean people who opposed the movement for African-American civil rights during the 1950s and 1960s, then some Southern politicians spring to mind. One is George Wallace, the Alabama governor who became the face of segregation in the South when he blocked the entrance to the University of Alabama to prevent African-American students from entering under federal protection. Another is Mississippi governor Ross Barnett, who took similar actions in response to attempts to integrate the University of Mississippi by James Meredith. Declaring that "God is the original segregationist," he, like Wallace, cultivated support among southern whites through his opposition to integration. Another very public opponent of the civil rights movement was Birmingham, Alabama city official Eugene "Bull" Connor. Connor basically abetted a violent response to the Freedom Rides in 1961, and most famously ordered city police and firefighters to attack protesters in the streets of Birmingham in 1963. The irony is that the intransigence of men like Wallace, Barnett, and especially Connor actually backfired on a national level. Americans sympathized with civil rights protesters, whose nonviolent methods contrasted on television with the response of souther segregationists. Indeed, the strategy of leaders like Martin Luther King, Jr. depended on their violence, which led to calls for federal civil rights legislation.