Eggman's programming
I know this has been mentioned before, but isn't it so weird that Eggman programs emotions and personalities into his robots??
People point out that this is really self destructive on his end because it can lead to some of his creations turning against him after building resentful emotions toward him, like Omega, Gamma, and all of the robots on Scrapnik Island.
My personal headcanon behind his thought process is that not even pure mechanical obedience can rival the loyalty a creation will have to its creator, or "father." It doesn't matter if you reprogram or rewire its entire structure to have its own free will if it's inherent personality, aspirations, and deepest desires will always be to make eggman proud of them, because of the way he's designed and conditioned them. They'll always return to him no matter how many chances you give them, because he's made it so that their biggest desire is to make him proud, even when given free-will or reprogrammed.
We see this most clearly with Metal Sonic, and Sonic will even tease him and take digs at him for it in the comics, telling him to "run home to daddy" (cringe). Clearly, even the characters in-story can see how eggman has raised all of his creations to depend on him for any sense of self worth or purpose. Truly evil, and I think something that's always overlooked when discussing eggman. People say he's not a respectable villain but I think this is really compelling and a unqiue way for a villain to function. Especially because his design is pretty dad-like to begin with, with the mustache, glasses, round body, and bald head lol.
It's so effective, that even when Metal Sonic gains even more power than Eggman through becoming Neo-Metal, he still only wants to take over the world to gift to Eggman. His influence even goes past his creations and gains loyalty from other aspiring inventors, like Dr. Starline.
Most of all, I think it's so effective because it's genuine. He really does love his creations, but simultaneously holds them up to impossible expectations and holds severe disappointment in them when they fail. I mean, think of it. Isn't it awful to design a creation that entirely depends on you for any feeling of worth or purpose, and to make it capable of love and such, only then to neglect and abandon it when it doesn't live up to your impossible standards? Just think of Scrapnik Island and the sheer amount of abandoned bots there.
I think after seeing Mr. Tinker and Belle, it raises the question, does Eggman deep down just want to foster these fatherly connections? To build childrens' toys and fun-rides and kiddy amusement parks, with his helpful heart-filled robot creations? He does often say that he only wants to take over the world in order to "enhance it" with technology, and that people just aren't cooperating. Maybe somewhere down the line his pure intentions got corrupted somehow into this extreme need for absolute control.
That is EXACTLY what I mean thank you @chaoxfix
Let's think about it: mechanical obedience means nothing when your opponent has a genius sidekick that's just as technologically advanced as you. Absolutely any weapon Eggman builds can be turned against him by Tails with a little bit of re-wiring. The solution? Give them emotions that overpower their programming, and make them complex and intense emotions that will always end in loyalty towards you and you alone. He's seen robots who overpowered their programming through love like Gamma, it seems to be a trump card that tops all other control, so why not design it in a way that'll make them love only you? The result: daddy issues. Give them just enough love to get them attached, then just enough harsh words and punishment to make them scared of losing you, to make the love feel rare and like it's something they need to work for.
In the fandom space and in the tags I saw @measlyfurball13 asking: If Eggman seems to purposefully take on a fatherly role with his creations, this makes one wonder, does he have the capacity to be a good dad?
The canon answer: Yes. According to the IDW comics. When he experienced amnesia, he still wanted to improve the world through technology and build eggmanland, but he wasn't obsessed with control, and operated on a much smaller scale. He just actually genuinely improved a village with his technology. He also created Bell the tinkerer, a puppet themed fixit robot who adamantly identifies as eggman's daughter and is broken up to tears over losing what she said was a really good father that she loved dearly.
And now with the introduction of Sage in Sonic Fronteirs, this pushes my thoughts even further. Sage overpowered Eggman's orders too, in the name of protecting him, out of a love for him. Eggman also clearly cared for her too, just as he does for metal sonic, and just as he did at one point for Bell. I do believe he has it in him to be a good dad, but something happened to him that has made him totally obsessive over having control. As we saw from the zombot arc, he fully believes he needs to have absolute control of everyone, and that they need to follow his commands like robots, or else he can't "improve the world." I think this need for control bleeds into his creations, and causes him to put up such high standards and expectations for them, and to behave so cruelly toward them when things don't turn out right (and they rarely do).
@curetapwater also added the thought: Could Eggman be inspired by Gerald's treatment toward his creations?
He seemed to behave in a fatherly way toward his own creation too. Letting Maria build a relationship with Shadow, letting Maria name him, leaving a video-diary for him where he called him son (in the Archie comics). I think this is why Shadow tends to defect to Eggman too (in sonic adventure 2, sonic rivals 2, the Archie comics, and the boom cartoon). He reminds him of Gerald, and so he wants to work with him, but in the end Eggman is a little too far gone. Shadow probably misses his father figure and sees him in Eggman. On the flip side, while archie Shadow sometimes defects to eggman's side, I think IDW Shadow is so aggressive toward Eggman for the same reason. I think seeing Gerald in Eggman really affects him, and causes him to act out and get more impulsive and aggressive. In his mind, he probably just wants Eggman gone once and for all so that he doesn't have to see someone so similar to Gerald committing such atrocious acts of evil.
I'd also like to point out that Gerald literally augmented Shadow's memories and put like,,, sleeper agent trigger phrases in his mind... and somehow put Maria's soul in him and emerl from Sonic battle. Nobody has pointed out how fucked up that is... that's a little fucked up. He edited Shadow's memories to make him believe that Maria wanted him to take revenge on the world, knowing how much he loved Maria and that he shared her soul and therefore the pain of her death. He knew this love would overpower absolutely any other attempt to control him, no one would be able to stop or sedate him unless they said something similar to Maria's last words and caused him to remember what she really wanted. Another case of love seeming to have absolute control, and therefore, if you hold control over their love and use it as a reward and punishment system, then you have absolute control over your weapon. We see the same with Emerl, he's supposed to be loyal to the most powerful person as a weapon, but instead Gerald managed to give him some free will through love or Maria's soul or what tf ever. So them if anyone actually tried to use him as a weapon, he would then self destruct out of his love for others and desire to keep the world safe from himself. In both games it's shown that Eggman went through Gerald's diary and work-notes, so it's very likely he could have learned a thing or two from him.
Also!! Shadow's self titled game where he learns to have a healthy sense of self worth that doesn't depend on anyone else's love is a really good continuation of this whole thing in my opinion. That's the dangers of depending on someone for love. Wether it be a parent, a sibling, a teacher, or even your hero. You have to have love for yourself, that's true freedom.