He has been called a reckless ultra-leftist, a loose cannon and an irritation to business, but for millions of South African workers, he is a hero, a beacon of hope for the poor.
He steadfastly refuses to join the waBenzis in government, but is likely to show up in a luxury sedan or a hired Mercedes Benz.
He has refused any major salary increase, going home with around R7 000 a month - but makes up for it with the union's credit card.
He battles to pronounce words like "unilaterally" but has an astounding technical knowledge of economics.
This is Zwelinzima Vavi, the political paradox who now stands to serve as general secretary for an unprecedented fourth term when Cosatu holds its 10th conference tomorrow.
The 10th child in an impoverished family of 12 from the Northern Cape, Vavi did not even know his birthday until the priest who baptised him informed him of the date - December 20, 1962.
His career in the union movement started in 1984, when he was working as a clerk on a gold mine.
Vavi has been applauded for standing firm on workers' rights, and lambasted for speaking like ANC Youth League leader Julius Malema. He once accused government leaders of promoting women in order to sleep with them.
The workers have always trusted him, voting him into power for three consecutive terms after he was first elected secretary-general in 1999.
Most union affiliates see Vavi's continued tenure at Cosatu House as bringing stability to the federation.
"South Africa needs him and that's why (we) argued that he should not go to cabinet, because the working class would have lost out. You still need a leader like him in Cosatu," says National Union of Metalworkers (Numsa) president Cedric Gina.
Mbeki once lost his cool publicly at a Numsa gala dinner, throwing his hands in the air and grinding his teeth, after Vavi likened his administration to Nazi rule.
But former South African Democratic Teachers Union (Sadtu) general secretary Thulas Nxesi says Vavi "is forthright, the type of leader you need, especially during these difficult times".
Vavi's colleagues agree he is a man who is adored by many and feared by others.
Nxesi recalls an incident which he says epitomises Vavi as a "principled" and "selfless" leader. After a heated three-hour debate which threatened the fragile unity of Sadtu - over whether to become a Cosatu affiliate or remain independent - a youthful Vavi advised his comrades to rather remain autonomous and united than risk polarising the workers.
He advised delegates to go back to the drawing board to decide what was best for them.
A year later Sadtu affiliated to Cosatu.