United States executed 46 prisoners last year.
Forty-four were executed by lethal injection, one by electrocution and one by firing squad, says the latest report by Amnesty International.
The US has executed 1,234 prisoners since the US Supreme Court lifted a moratorium on the death penalty in 1976.
Brandon Rhode was executed in Georgia on 27 September, six days after he slashed his arms and neck with a razor. He was brought back from the brink of death and killed by lethal injection for a crime committed when he was 18 years old.
David Powell was executed in Texas on 15 June last year, more than three decades after his crime, despite compelling evidence of his rehabilitation, says Amnesty International. He had been on death row for more than half of his life.
Holly Wood was executed in Alabama on 9 September. At his trial, his inexperienced lawyer had presented no evidence to the jury of Holly Woodâ€™s significant mental impairments.
Jeffrey Landrigan was executed in Arizona on 26 October. Over the years, 13 federal judges argued for a hearing into the failings of his trial lawyer.
The execution went ahead after the US Supreme Court voted 5-4 to lift a stay imposed by a lower court concerned by the stateâ€™s refusal to provide adequate information about one of the lethal injection drugs â€“ of which there was a nationwide shortage â€“ it had obtained from a source overseas.