When the South African track star Oscar Pistorius stood trial for the brutal killing of his girlfriend, he hired Bell Pottinger, an aggressive British public relations firm, to try to smooth his tattered reputation. President Bashar al-Assad of Syria and his wife turned to the firm for help in recasting their image. So did Aleksandr G. Lukashenko, the dictator of Belarus.

In the fraught world of image makeovers, Bell Pottinger stood out for venturing where others feared to go. It courted embattled governments, controversial clients and powerful people who ran afoul of public opinion. Along the way, it reaped hefty fees and became one of Britain’s most influential public relations firms.

But on Tuesday, Bell Pottinger came crashing down after its latest effort, in South Africa, spiraled into disaster. The firm was forced to appoint administrators for its British operations as clients, employees and a major shareholder cut their ties to the firm.

Bell Pottinger’s swift downfall sent shudders through the public relations industry and raised questions about the increasingly combative tactics used by those who engage in what critics call “reputation laundering.”