Episode 18: Shinya's farewell letter to Akane and Akane's reaction.
Episode 19: the picture of little Ginoza sitting in his father's arms.
As well as Ginoza taking out his frustration on Masaoka that the people close to him (his father, then his partner) keep abandoning him for 'the other side of the law', and desperately trying to figure out what ideals everyone else holds that are worth sacrificing their family and career. Puts his concern with Akane's dangerous behavior throughout the series in a new light...
Episode 21: Masaoka's death and the reactions of both Ginoza and Kogami. Kogami just becomes more determined to hunt down Makishima, but Ginoza completely falls apart and takes it so hard that the next time we see him, he's become a latent criminal and reevaluated his perception of justice.
Ginoza: (after Masaoka releases Makishima and sacrifices himself to save his son) What kind of detective are you?!
Episode 22: Akane's face when she realizes that she's failed to keep Kogami from killing Makishima. It's a look of utter heartbreaking despondency, as she realizes her plan to try bring Makishima to justice while saving Kogami from being marked for termination has completely fallen through and that she's utterly failed in her mission.
In particular, the look on Akane's face when she wakes up and sees the spent cartridges from the revolver falling in front of her. She knows what's about to happen but is too jarred from the crashed truck to get up and try stop Kogami. She can only pitifully plead as Kogami heads off to gun down Makishima.
Makishima's death itself. It begins with him claiming that everyone is alone and that all relationships are replaceable, though, as he begins to cry, he wonders if there was was anyone other than Kogami who could kill him. His last words consist of him pitifully asking Kogami if he will find a replacement for him.
Also in that same episode, Ginoza ruefully notes that Section 2 has been ordered to abandon their search for Kagari. He then reveals that he doesn't really think Kagari is alive anyway. The sad part is that Akane knows for a fact that Kagari is definitely dead, but she can't tell Ginoza he's right without compromising the true nature of the Sibyl System, so she sadly keeps quiet about it and quickly changes the subject to start talking about Kougami and where he might be.
In episode 2 of season 2 we learn that Akane lights cigarettes but doesn't smoke them, this shows how much she misses Shinya who would smoke all the time.
In episode 4 of season 2, Aoyanagi's death and the slaughter of the civilians by the police. Doubles as Nightmare Fuel.
In episode 9 of season 2, the fate of Aoi Tsunemori, Akane's grandmother. Gets her ear cut off and delivered to Akane and then killed by Tougane in the trunk of a car by a Dominator no less.