I genuinely think Kylo Ren stands out to me because his character starts at an interesting place. He’s a flawed villain right from the beginning of this new trilogy. Don’t get me wrong, I love Darth Vader, but we’ve already seen his character type in Star Wars. The type of villain that already has shit together, just about flawless. Hell, even the PT had this. Count Dooku? Darth Maul? Grievous to a degree. Basically, those other villains were already trained and in their ‘prime’.
Now though, we may see a struggling villain struggle more to attain a respectable reputation. Basically, Kylo Ren could be that transitional Vader character between Episode III and ANH. We don’t know to what lengths or ease Vader gained that menacing reputation in the galaxy AND within his own Empire, but I imagined it wasn’t instantaneous. So what COULD make Kylo Ren interesting is if we see him go from a ‘weakling’ (in comparison to Vader) to stunning badass.
The new trilogy may screw this up though for all I know.