As I stated in my main write-up for Ep. 79, Subaru’s Authorities are shaped by the biggest regret of each of those who reside in the dark world (Relevant scenes of the dark world being when Subaru remembered being in the dark world with his heart caressed by Satella in Ep. 8 after Puck used Shamak on him, when Satella whispered, “Aishiteru” to Subaru during the White Whale fight in Ep. 20, and when Subaru saw both Petelgeuse and Regulus before seeing Satella in Ep. 70) with Regulus’s biggest regret being that his first wife smiled in her final moments, showing her unhappiness with being his wife, and therefore, he desired to be able to share how he felt about her with her ’cause she never knew that he genuinely cared for her even though he slaughtered her family and the village the two lived in, and since communication is a two-way street, and Regulus wouldn’t have known to think to tell his first wife about his love for her had he not known about his first wife’s dissatisfaction with him, Subaru’s power likely manifested in being able to take what others feel inside their heart and feel it for himself, which is how he felt the warmth of Rem’s love she imparted to him to stop him from spiraling, in addition to sharing what he feels with others (unconfirmed for now). All of this was due to Regulus deep down desiring human connection, which he ultimately failed to do with his wife.
This is not to say that Regulus is meant to be seen as a sympathetic character as he was a horrible guy who did many wretched things, but as can be seen by his rambling to himself in Season 3, the guy had serious trauma over his wife smiling in her final moments even though no matter what he’d done before that, she’d refused to smile, showing that her not smiling was not for a lack of trying on his part. That trauma’s why he forced his future wives to agree to never smile or face death ’cause his first wife actually meant something to him. I believe Regulus was coping in saying that he never needed for them to smile ’cause many people who have trauma create incidents that will re-traumatize them, meaning if Regulus lived long enough, he’d have another wife who smiled in her final moments.
There’s literally empirical evidence of trauma survivors creating incidents that re-traumatize them. Drawing on that knowledge, this is why Kana from Oshi no Ko is obsessed with Aqua, ’cause when he shined a light on her during the Sweet Today adaption arc, she replaced her mother, who used to be the one who validated her talent and feelings of competence, with Aqua, since he stepped into that role for her even though Aqua’s very emotionally distant to the point that her fixation with him led to a proximation of emotional abuse (not actual emotional abuse) when he started ghosting her. And also relevant is that Aqua’s mother, Hoshino Ai, the person he most wanted to support, was a popular idol who died, and he was subconsciously drawn to making this similar situation by having Kana, the one he most wanted to support, join her sister’s idol group, and when someone pointed out that connection, he was distressed about potentially reliving that and his own role in potentially re-traumatizing himself.
This is backed by Regulus stating Subaru violated his rights as an unselfish man who desires nothing but to settle for a tiny bit of simple, ordinary happiness, which shows Regulus most likely just wanted a wife who loved him even though he killed everyone his first wife knew, which is why she never showed emotion and wouldn’t smile no matter what he did with him coping by telling himself he never needed them to to since it makes their faces uglier after she died. He realized he was the reason she was unhappy, and he ragequit life after that and never decided to be a proper man due to subconsciously realizing how he fucked up, and his coping mechanism for this trauma is blaming everyone else for his issues and never take accountability for his first wife’s unhappiness to help him cope with his failure even if that appears to be an oxymoron ’cause the reality is, accepting that he did his first wife bad would mean that he was such a disaster who made the only person he held dear live a life of despair, and accepting that might’ve resulted in him deactivating his Authority and considering suicide, meaning his coping mechanism’s the only thing that kept him alive up until the end of Season 3.
Some people with deep psychological wounds/traumas are known to recall traumatizing things in their final moments, and this would explain why Regulus was haunted by his wives smiling at him when Reinhard sent him up into the sky and then remembered young Emilia and how she’d been protected by Fortuna and Regulus ’cause at the time seeing Fortuna and Petelgeuse, a real example of both romantic and familial love, reminded him of his own failure as a husband, which is why Regulus attacked Pandora when she told him to calm his anger ’cause just the thought of Fortuna and Petelguse incensed him by reminding him of how inadequate he is as a person.
As for Petelgeuse, his deeply regretting killing Fortuna is probably why Subaru gets recoil from using Invisible Providence offensively since that act hurt him so much and drove him insane after whatever Pandora told him to help him cope with what he did, and we know it did given Petelgeuse was talking about how Subaru killed Rem in Arc 3 with his own hands with tears in his eyes, showing that the moment in which Petelgeuse killed Fortuna with his Unseen Hand hurt him to his core. This would be why Subaru wasn’t hurt when he merely entered Invisible Providence into Emilia’s body but was pained when he crushed Regulus’s heart and why he wasn’t pained when he rubbed Joseph’s neck with Invisible Providence.
Even Petelgeuse killing Rem in the brutal fashion he did was likely ’cause he deep down remembered how he killed Fortuna and was driven, without intentionally doing so, to make that connection ’cause trauma survivors tend to put themselves in situations that re-traumatize them, which is why he was crying in that scene as he realized what he had did to Fortuna.
Anyway, I’ll leave it at that. I had neglected to delve into this completely for my main write-up, so I felt I needed to do this.