ANC presidential hopeful Nkosazana Dlamini-Zuma has spoken out against the toxic influence of some leaders within the ANC, but did not mention names.“You should not [seek] vengeance when you are a leader, but you must talk things over so you lead with a clear mind,” she said delivering the Nelson Mandela Lecture to a packed Pietermaritzburg City Hall ahead of the Mandela Day Marathon on Sunday.She also criticised ANC members who took their grievances to the media instead of raising their concerns within the party’s structures. “Why be so bitter until we kill each other, like is happening currently?” she asked.Dlamini-Zuma said ANC leaders such as former president Nelson Mandela, who spent 27 years in jail, were not bitter towards white people when they were released from incarceration. “You can’t use a personal vendetta to destroy the organisation,” she warned, adding that leaders had to have integrity and be dependable.Addressing the question of who would succeed her ex-husband, President Jacob Zuma, she said ANC leaders were elected democratically. She called for the ANC to remain united after its elective conference in December.“Where do some leaders get [the idea] that when contesting positions the ANC would be divided?” she asked.ANC members should follow and respect whoever was victorious after the conference, she said.“If you want to be a leader, be prepared to be led. Branches will choose. We can’t please every faction.”The main contenders for the party’s presidency are Dlamini-Zuma and ANC deputy president Cyril Ramaphosa.Dlamini-Zuma said the ANC had to win the 2019 general elections, irrespective of who was chosen to lead the party.She suggested that the implementation of radical economic transformation would not be a difficult task and said it must be welcomed.“Blacks and whites must be happy about radical economic transformation because it will bring investors and create job opportunities for the youth.”White monopoly capital had to be dismantled to allow the marginalised to play a role in the economy, she said.“We are not chasing them [white people] away from the country. We must also get land to build houses and our industries. All this needs money. "Money is in the banks. More banks should be created to help us,” she said.The DA would not transform the economy for the benefit of black people, but the ANC would, she said.