The memories Adora and Catra go through in Episode 11. Given Light Hope's instructions to Adora to give up all her friends, and the fact she appears as soon as Catra betrays Adora, perhaps she was using them to try to drive the two apart. The Reveal in Season 4 that Light Hope has been manipulating Adora so that she would activate the Heart of Etheria to destroy the First Ones' enemies gives a lot of credence to this theory.
Some fans have also theorized that Hordak might have been much more aware of Catra and Shadow Weaver's actions than he let on, and subtly pushed them against each other so that they wouldn't join forces and overthrow him, leaving Catra an Unwitting Pawn through most of the story.
Scorpia's possible Transparent Closet case. Given what's seen of the Horde's mentality (no displays of physical weakness), some think Scorpia is determined to be Catra's "best friend" because, thanks to being raised by the Horde, she doesn't actually know she's got a romantic crush. This may have been torpedoed by a photograph in Season 4 showing she has two mothers.
Micah, Adora, Catra, Glimmer — did Shadow Weaver ever truly care for any of them, or does she just like being a controlling mentor/parental figure and needs others to play the part in her power fantasies? All four of those relationships have evidence one way or the other. For what it's worth, Catra and Adora both call her out as the latter in Season 5, but then in the finale she goes and performs a Heroic Sacrifice to save them.As part of said Heroic Sacrifice, Shadow Weaver takes off her mask and looks upon Catra and Adora as herself as she tells them she's proud of them. Did she truly mean it, or was she just giving them the small bit of peace that she could provide before she died? Or was it one last selfish act to try and redeem her reputation in the eyes of her "children"? ND leans toward it being some of both.
Should Hordak be seen as an evil man because of his conquest and tyranny, or is he less culpable because he's a product of indoctrination and oppression? As a clone in Horde Prime's army, Hordak was born into a hyper-militaristic culture in which conquest was his only reason for existing, and any dissent would have gotten him killed. After the revelations of "Destiny, Part 2", the degree to which he had/has free will and to which he's acting on his programming is also up for debate.
In Season 4, when Hordak leads troops from the frontlines, is he doing so because he genuinely enjoys being back on the battlefield, or because he's hoping to see Entrapta? Is it a little of both? Similarly, in Season 4 Hordak never does anything to protect the crystal powering his exoskeleton, allowing Catra to defeat him twice by ripping it out. Is that due to his inability to adapt to new situations, him not wanting to modify one of Entrapta's last creations (particularly one she defined as her greatest work yet), or a sign of his increasing desperation leading him not to care about his own safety?
Hordak's lair is dark, dirty, and industrial, a stark contrast to the bright, clean, sleek designs of Horde Prime's technology. Does Hordak fashion his lair in this manner because he lacks the materials and ability to make it more aesthetically pleasing, or because he was always intent on getting back to Horde Prime and this was just a temporary base of operations? Or perhaps Hordak subconsciously made his base look as different from Horde Prime's as he could as a reflection of his independence and estrangement.
Catra in general inspires a lot of this by the end of Season 4. Was her telling Horde Prime about the Heart of Etheria yet another attempt to earn validation by getting in the good graces of the most powerful person around, or was it actually a desperate maneuver aimed at saving herself, Glimmer, and all of Etheria from otherwise certain death? Did Double Trouble's Breaking Speech actually get her to recognize her self-destructive and toxic tendencies, leading to her protecting Etheria, or did it just drive her further into nihilistic fascism, leading her to allying with Horde Prime? Season 5 seems to indicate Catra only agreed to serve Horde Prime out of fear for her own life.
Did Double Trouble ever care about Catra, at least a little? They seem to genuinely enjoy her company, but remind her that they're here mainly because they're getting paid, and, true to their word, they defect for a better offer later on. Furthermore, was their Breaking Speech to Catra just to further twist the knife, or were they being honest when they said it was For Your Own Good, laying down some very brutal truths about Catra's flaws because someone had to — albeit, enjoying it a little too much while they did it? For whatever it's worth, DT's voice actor has said on their Twitter that they believe DT does care about her, at least enough to be honest.
Light Hope. We do find out that she and Mara had a friendship, but her benevolent personality was violently overridden by the First Ones' reprogramming so that she can activate the Heart Of Etheria, but the parts of her that are good have been attempting to resist. That being said, why did she really choose Adora? It depends on which programming of her took the initiative—was it the remnants of her benevolent self that chose Adora because she needed the new She-Ra to be strong-willed enough to be able to destroy her when the time comes? Or was it her reprogrammed self following her creators' directive to find the next She-Ra to activate the Heart of Etheria?
that Hordak might have been much more aware of Catra and Shadow Weaver's actions than he let on, and subtly pushed them against each other so that they wouldn't join forces and overthrow him, leaving Catra an Unwitting Pawn through most of the story.