The most credible evidence against Brand comes from a woman named Nadia, who said she was raped by him in LA in 2012. She went immediately to a rape centre afterwards & there are medical records which corroborate her account. She also spent 5 months in counselling after the incident (which there are records of) and contemporaneous text messages from Brand in which he says he was "sorry."
The below accusation, from a woman in Britain, which led to a conviction didn't have the physical evidence. But there were 2 dozen witnesses who corroborated her story, & similarly there were contemporaneous text messages from Brand apologising for what he did.