This is a quote by a famous historian, Lord Acton, who lived from 1834 to 1902 and was Regius Professor of Modern History at Cambridge University, in England.
He warned that power corrupts people -- in other words, people who have power (he was thinking of political leaders) may turn bad and start to misuse their power. "Absolute" here means "total" or "complete". If people with power turn bad, people with complete power may turn completely bad.
Since this is a well-known quote, if you need it for a translation you should first look to see if it has already been translated. There may already be a well-known translation in use which you should also use. Search Google for "Acton" and the word for "power" in your language.