Durarara!!x2 Episode 16 (or 4) - A Rumor Only Lasts Seventy-Five Days
Finally an episode that isn't terminally boring.
In one of the LNs Rhyogo Narita talks about how he was surprised to see everybody thought of Mikado as the lead character, and it really shows here. Outside of the opening credits, he's appeared for all of 5 seconds, and I can't help but feel the franchise might have been vastly improved by keeping the focus more tightly on him and the original core of characters, as (with the exception of the children) none of the newly introduced characters are as likable, charming or interesting as the original core.
Also the whole expansion into the Awakusu Company, leads to a loss of narrative clarity that makes the show feel distinctly muddled and directionless, and this is probably the most disappointing part of x2 for me, large parts of the show just seem to be going nowhere. Maybe there will be some eureka moment where everything clicks, but the more it goes on (and having read some of the LNs), that seems like it's never going to happen...