The ending of the Fire Red LP. After Sammy defeats the Elite Four for a second time, Chorocojo admits he doesn't have a good ending for Sammy and her team. Instead, he goes through a series of shout outs to older video games using Sammy and her Pokemon, before finishing with a shot of the seven of them curled up infront of the Wii, asleep.
Lake Acuity in the Platinum LP. Lady has spent the entire trip up to Snowpoint complaining about "saving my idiot", but when she finally reaches the Lake and Jorge talks about not being able to save Uxie...
Lady: Welp, a certain group of people are at the top of my list now.
Really, a lot of the subtle ways Lady's character has changed by the end would fall into this category. She essentially goes from a relatively jaded, snarky, and reserved person to somebody who cares for her friends and on a whole seems far more satisfied with life in general.
Lady: Man, I've been upbeat lately. I wonder why that is?
Haley from the Black LP, who spends a good deal of her time simply trying to enjoy herself with her friends, getting riled up when Team Plasma steals Bianca's pokemon, exchanging friendly encouraging banter with Bianca and Cheren during battles, and telling N to back off when he reveals he's been checking in on them.