Well I think it's probably because Rey was simply much stronger in the force than the students were, and maybe the strongest since Luke-- or otherwise they wouldn't be centering an entire new trilogy around her.
Maybe he's not as fearsome by the end as he was early on, but he still killed freakin Han Solo, so that still makes him pretty darn hateable and villainous in my book.
I don't know DJ.
There's something to be said for Rey and her Force powers. Both Anakin and Luke were extremely powerful with the Force in their respective sagas. That being said they were also overmatched at the beginning of their journeys. Heck, even Lucas didn't put young Anakin against Maul. And Anakin also lost against Dooku the first time out. Lucas also didn't put Luke against Vader in ANH and Luke also lost the first time they fought. Abrams upended that poetry when he had Rey defeat Ren. Now it makes me wonder if there is another more powerful Force user waiting in the wings. I know there's Snoke, and I suspect that he and Luke will go at it in the next film. And perhaps Snoke will kill Luke and set it up for Rey to avenge him. Or Rey and a newly motivated/better trained Ren will go at it in the second film and the third.
Until I see more of Snoke I don't fear Kylo Ren where Rey is concerned. I think she's only going to get better and Ren might too, and he might even defeat her the second time out. It's just that fear is gone now. If I recall Ahsoka took on Grevious in the Clone Wars and while Grevious was a joke in ROTS, I had to respect his reputation as a fearsome Jedi killer so when he faces off against Ahsoka you wonder, how is she going to survive? That's what's missing now between Rey and Ren. She needs a challenge worthy of her. And I think Ren is not it. The total geek and Sith fan in me wants to see Darth Plagueis (Max Von Sydow would've made an awesome Plagueis) or Darth Maul again. Man, Maul vs. Luke for example, now that would be epic.
Killing Han is big no doubt and he'll go down in a villain's hall of fame for that, but it's not just the act. It's how you do it. I mean when you had Maul just slice through Qui Gonn or Anakin about to slaughter the younglings or Anakin going to slaughter the Sandpeople there was a brutality there. I didn't quite get that with Ren killing Han. I know its supposed to play that way, that Ren had made his choice. That he had chosen the dark. However I don't buy that he's fully committed like Maul was already committed and like Anakin did after he swore his allegiance to Palpatine. I also think that Ren's conflict will play a key role in his arc over the course of the new trilogy.
