In that scene when L died, there was that one shot of Light's face where he looked saddened over it, not talking about the obvious parts where he was putting on a show for everyone proclaiming his revenge against Ren. But there was one shot where it only showed an up close shot of Light's face looking somewhat sad.
I know he was a psychopath and all but i always felt a small part of him was sad about L dying.
L was his friend and big counterpart.
The only one up there with him truly challenging him.
Beating him meant this all ended.
Yes. I think he clearly regretted that, to some degree.
Big spoilers ahead:
I actually felt like the post-L death stuff was bungled. They just replaced L with Near, who was another youthful, quirky, eccentric genius detective with seemingly limitless resources. It's never good, I think, for shows to just frost over character departures that way.
I thought it would have been interesting to see what Light would have done if he defeated L, ruled the world, but became bored and sullen. What he "wanted", what he got, was not what he really wanted. He'd realise he killed his only real friend, and become despondent and depressed. His actions with the Death Note would mean less and less, and his declining emotional and mental state would be his undoing as his father and the rest of the task force catch on to his odd behaviour and bring him down.
Could've been really neat to see the thriller/suspense aspects get turned inwards and Light became his own worst enemy. But they didn't. They just generated up a similar detective and ran the scenario again.
This is the main reason why I think post-L episode suffer compared to the L stuff. I did LOVE the final showdown stuff, though.