Darth Nox, Emperor's Wrath, Cipher 9 and the Champion of the Great Hunt runs the gauntlet. All of them as of Shadow of Revan.
Round 1: ROTJ Luke, Obi-Wan (Episode 4), Han Solo and Chewbaaca
Round 2: Arcann and Vaylin
Round 3: Anakin Skywalker CW, Ahsoka CW, Obi-Wan CW
Round 4: Kyle Katarn, Jaina Solo and Mara Jade
Round 4: Bastilla Shan, Meetra Surik, Revan (Novel, where he is drugged) and Lord Scourge
Round 6: Emperor Palpatine