Before we find out about his less than supportive tendencies, Derek doing that weather shout out to his fiancee was rather sweet.
After the break up, Susan finally realizes that being with the monsters has made her feel more fulfilled than she had in a very long time. Amazing.
Near the film's climax, when the other monsters tell a de-powered Susan to escape from Galaxhar's self-destructing ship, while they're trapped themselves. Susan refuses. Heck, much of the film's heart comes from the team chemistry between these characters.
In a less obvious example, the fact that General Warren R. Monger bargained with the president for the monsters' freedom in exchange for them fighting the giant robot. And making sure the Modesto PD didn't shoot at them when they went to visit Susan's parents. He's definitely gotten fond of the monsters over the fifty years of guarding them.