"Flashback" a time travel episode in which Virgil goes back to meet his deceased mother on the night she died in a gang riot as a paramedic/EMT caught in the crossfire whilst trying to save lives. Virgil reveals his secret identity as Static to her and begs her to stay out of harms way so she doesn't die this time, painfully explaining his reasons - though he doesn't explicitly mention she is destined to die but mentioning she will be hurt. However, her desire to help people drives her back onto the streets even though it's implied she has figured out why Virgil gave her such a dire warning. His panic as he sees her with her ambulance crew amongst the fracas as he is stuck in the time bubble that returns him to the future is heartbreaking, made even worse when he runs home with the faint hope he succeeded only to discover she still died.
Adding to that is the reveal of what did change: on the night she died, Virgil's mother told everyone how her son was a hero and she was proud of him.
In "Consequences", Virgil's showboating got his friend Daisy into a temporary coma during a fight with Puff and Onyx. He feels like it was partially his fault, which is sad to see a hero have this sort of problem potentially harming someone close to them.
"Jimmy" involves a depressed kid who gets bullied a lot. It gets worse when he brings a gun to the Community Center and aims it at his bully. Richie and Freda try to talk him out of it, and the boy is crying. And as he's trying to put the gun down, the bully's goons tackle him, causing him to shoot Richie in the leg. This shocks the boy into curling up and sobbing. That scene always shocked this troper out.
There are 2 other really hard to watch scenes tied to the above.
Virgil ranting about how upset he is about the events; he's mad at the bullies for jumpstarting the whole thing, he's mad at Jimmy for shooting Richie in the first place and he's mad at himself for not doing more to stop it.
The exchange when Virgil is signing Richie's cast. While it's somewhat Played for Laughs, Richie remarking about if the bullet had hit just a little lower and Virgil very firmly telling him not to go there is hard to hear.
When Static and Hotstreak are chained together, they learn they're in a medical facility. Hotstreak totally flips out, eventually revealing that at one point, he spent two years in a hospital. This reveals a somewhat poignant side to his usual thuggish portrayal.
Virgil finding out about Mr. Foley's racism. It's blatantly clear that Virgil is deeply hurt (and not entirely on his own behalf; he's shown later to just be thrown by how someone like Richie can have a dad like that) and that Richie is devastated when his best friend leaves. Then the exchange where Richie snaps at his father about how he got what he wanted and that his best friend's gone before snarling "I hate you!" and disappearing into the streets to ultimately getting captured and held hostage by Ebon.