Darth Vader would own Maul without much problem imo based on everything I've seen and read. He'd have a much better time against Anakin but he'd still get owned at the end there. Kenobi was in a unique and advantageous position to defeat Anakin.
Vader was the John Wick of the galaxy. People were terrified of him, and rightly so. At the end there, even the Emperor started to fear Vader and the Sith his anger and pain had allowed him to turn into despite being more machine than man. He was lethal as hell. He was everything Anakin wasn't: unemotional, calculating and every move had a purpose.