If there is one moment in the entire series which crowned it, it's the end of the Fear Itself arc. The kids are forced to make a choice amongst themselves of who lives and who dies, with three of them willing to put down their lives for the others to stop two of the worthy. It never really topped that moment.
The Big Bad, Jeremy, doesn't believe that Finesse will really let him die, because she's an Avenger and hero. She replies by removing the bandages and reminding him that her, and the other students, were chosen because they were the most likely to become villains. As he's dying, she finished off with an echo of what he said earlier.