Ben Solo fully turns to the dark side as he kills his first individual, Ren, the leader of the Knights of Ren. After killing him, the Knights of Ren bow down to Ben as their new leader.
Interesting that even Rey, all the way back in Jakku, could feel his turn to the dark side without even meeting him.
Of course, the Palpatine clone had to make a cameo as well.
From – Star Wars: The Rise Of Kylo Ren #4