I'm going to be very unpopular.
Let's examine everybody's favorite villain, Darth Vader. Intimidating. Powerful. But not the most powerful. Maybe third, after Luke and Kylo. Then Rey. So Fourth. And possibly behind Kenobi, Luke, Windu, Yoda, Palpatine, or even Dooku, but I'll leave that alone for now.
So let's look at how he got there.
A freed slave, suddenly given a very enviable lifestyle, but unable to keep the promises he made (To the Jedi order, and to not betraying his wife and strangling her while pregnant standing on a volcano). And a poor teacher, who constantly endangers his apprentice, before she quits entirely. So then he swears to a new master on a promise of "together we might unlock the secret of immortality." So for the second time he goes on a rampage, killing "not just the men, but the women, and the children." With me so far? Ok. So now we have the biggest baddie in the universe. Who answers to Palpatine. Oh and also to Tarkin. And who is still unable to find Ashoka, yoda, or kenobi. Or detect the lie that his child(ren) survived. Still not powerful or trusted enough to be taught Force Lightning, though he can stop a laser blast with is bare (gloved) hand. Ultimately he is killed by his own master.
Hardly the biggest villain ever, even in his own story.
Then lets examine Kylo Ren. We can see that he is more powerful than his esteemed uncle from pretty early on, despite him not realizing it. We also see that he is more convicted than Vader, only leaving his early teacher after being betrayed, and not for some cradle robbing politician. Then he overpowers not just one, but two masters. Sure, Luke pulled a little sneaky, but the effort killed him. Also consider that Luke was scared of Kylo. Luke wasn't scared of Vader, in fact, he was confident in his ability to recruit Vader.
In a nutshell, there is my argument. Vader was possibly more cruel, and was bad for much longer, but Kylo was an all around better character. More powerful, more ambitious (a very important trait for any villain) and wiser.
Hate all you want, report me to the nerd authorities. Flag this as spam.
Or lay out a reasonable argument and try to sway me.