The Infernal is the father of a young girl who had also previously lost her mother to spontaneous human combustion. As the daughter cries, not only having lost both her parents to the same problem but also fearing that she might be next, the Fire Force enter the house, ready to fight... only to find that the Infernal apparently retained enough of his humanity to keep control of his actions, merely sitting at the dinner table looking at a picture of his wife and daughter and not actually burning anything. He doesn't put up any resistance as Iris recites her prayer and Arthur draws Excalibur to put him out of his misery. Even if he's in control enough not to attack anybody, he's still a 1st-generation Infernal and thus can't ever turn off his fire, so he still has to die.
May count as awesome and heartwarming as well. While sitting there, he's in absolute agony, experiencing the feeling of being burned alive that entire time. Infernals lose their sense of humanity mostly to the insanity of that agony. He had enough force of will to not only to bare and endure the pain, while controlling his flames so he doesn't cause any destruction, but to do so all the while waiting patiently for his daughter to come home; maybe so he could at see her one last time and perhaps say goodbye to her. He then patiently awaits the Fire Force to come and put him to rest - and free him from his agony - and doesn't resist or fight them - probably knowing that his release from pain is soon at hand. He did all of that, out of sheer force of will and perhaps love for his child.
Episode 9: Tamaki goes through quite the emotional ringer. Not only is Rekka, the Captain she admired, a sociopathic Serial Killer responsible for many innocent people becoming Infernals, but is also an agent of the White Clad. Her insistence at staying by Rekka's side during his "prayer" only gets her squeezed unconscious, but when she wakes up, she witnesses Rekka turning children into Infernals in his attempt to look for a vessal for the Pilot's Light. Horrified, Tamaki slaps Rekka and tries signaling for help, but the now enraged Rekka proceeds to stomp her into the ground. As Rekka prepares to roast her alive, Tamaki is reduced to weakly pleading for help... when Shinra suddenly flies in and stomps Rekka's face. The cherry on this sad cake happens when Shinra asks Tamaki if she's alright — the poor girl bursts into tears at Shinra's presence and frantically shakes her head.
Season 2
Episode 2: Although Arthur doesn't act like he minds, the revelation that his parents both abandoned him is still sad.
Episode 12: After 5-2 escapes the Nether, he finds himself taken in by a kind, loving family of three. But when he comes home from a shopping trip, he finds all of them having been murdered by the Holy Sol Shadows. The silent pain and shock on his face upon seeing the bloodbath speaks volumes.
Episode 17: Nataku's cold upbringing by his parents who only showed affection when he gets perfect grades on his school work, and scoldings on anything less than perfect. He felt less like a child and more
