By Lisa Richwine (Reuters) – Actor Johnny Depp returned to the witness stand on Wednesday to refute ex-wife Amber Heard’s testimony in their defamation battle, saying the abuse claims she leveled against him were “unimaginably brutal, cruel and false.” The “Pirates of the Caribbean” star, 58, sued Heard for $50 million and argued that she defamed him when she called herself “a public figure representing domestic abuse.” Heard, 36, has countersued for $100 million, saying Depp smeared her when his lawyer said her accusations were a “hoax.” On Wednesday, Depp and his attorneys worked to rebut He…