Basic Trope: A death of a single important character matters more than thousands of Redshirt Armies.
Straight: Through the course of the show, we see many Mooks and Red Shirts being killed by both the heroes and the villains, either for the sake of defense or because they have outlived their usefulness. But when Alice gets killed cold-bloodedly by the Big Bad Emperor Evulz, all her teammates suffer from Heroic BSOD and mourns for the next few episodes, which was Emperor Evulz' Batman Gambit to slow them down.
A character watches an entire planet blow up and suddenly bursts into tears... because it means his pet bug died.
Jeff reacts this way after spilling juice on his shirt.
Downplayed: The heroes do sometimes think about the many people (whether it be Mooks or Redshirts) who died because of necessary actions or Emperor Evulz, but then realize that, to defeat Emperor Evulz, some must lose their lives. They just couldn't deal with Alice's death the same way.
Justified: Alice was a helpless prisoner when she was killed.
The heroes could care less when Alice or another teammate dies or goes missing, but deeply mourn when people they hardly know lose their lives.