Emma had no great love for Erik either. From the moment she met him she disliked him. If he had a stronger mind, he would have seen that Sebastian only did what he did for the betterment of mutants. Sebastian's methods may have been unpleasant, but no one could deny they had made Erik stronger. Erik himself had admitted Sebastian had made him stronger. If Erik didn't let his heart rule his head, Emma thought he would see that. Pathetic. That's what Erik was: pathetic. He and Sebastian could have worked together. But Erik let his emotions get in the way of what he and Sebastian both wanted.
Sebastian never hated Erik. He had worked in Auschwitz desperately waiting to find any prisoner who showed signs of being a mutant. He had his fun with several prisoners before Erik. But none of them had been mutants. He wasn't fully able to test his hypotheses. He used them to perfect his methods, but mostly he just viewed them as a way to pass time. And then he saw that small boy bend that gate. He viewed Erik as a gift. He was thrilled to finally have a fellow mutant to test his hypotheses on. It would be for the betterment mutantkind. He wanted to help Erik and all mutants unlock their full potential.
Erik did not disappoint him. He proved Sebastian's hypothesis that emotions could be used to channel one's mutant ability. He had never guessed just how effective anger could be in that capacity. He knew fear could be manipulated for power, which he planned to use to his advantage, but Erik's anger was easier to channel than his fear. Of course he had fun with Erik, but that had more to do with what he was learning and less to do with watching Erik suffer. Erik viewed Sebastian as a madman who enjoyed inflicting pain. But in reality, he was a genius who enjoyed creating a future for mutants. Sebastian knew Erik was too young to fully grasp his view for the future, but he had hoped that Erik would come around. He truly wanted what was best for all mutants, including Erik.
Emma understood that. She understood that sometimes extreme methods were necessary. She loved that about Sebastian. He didn't do what made everyone happy. He did what he had to do. He was the only man Emma ever loved. As a telepath, she knew that most people were pathetic like Erik: not willing to do whatever it took, and not able to look past their emotions. Sebastian had been different. He displayed a cold logic. He truly had a vision for the future that Emma knew was beautiful. It didn't hurt that he was charming and cultured. Or that his view of the future included Emma as his queen once she had proven herself loyal to him. Emma had dated men before, usually just to use them for her advantage. But what she and Sebastian had was special.
In the 60s, men usually didn't see women as anything important. But Sebastian was smart enough to see past things like gender and race. He may have aligned himself with the Nazis, but that was only out of convenience. He used their foolish prison camps as a base for his research. He didn't agree with their definition of a superior race. Though he had a respect for their military tactics and their common willingness to do anything for the future they aspired to, he knew their view of superiority was flawed. Sebastian had been ahead of the times like that. Emma loved that in him.
Though Erik never admitted it, Emma knew that deep down he knew Sebastian had been right. He said it himself. He agreed with Sebastian's words about mutant superiority. Honestly, Erik took it further than Sebastian. Sebastian merely thought humans were meaningless. Sebastian basically viewed humans as an obsolete model. He viewed them as a horse and buggy compared to the car that was mutantkind. Erik hated them. He believed that the average human was ignorant and fearful. Emma agreed with Erik that humans would try to fight against mutants, but she disagreed with Erik's fear. Erik was afraid of humans. He was afraid they would oppress mutants the way those Nazi idiots had oppressed him for being Jewish. That was the root of Erik's motivation: though he truly believed mutants were superior, he didn't care nearly as much about that beautiful vision as he did about protecting his fellow mutants. Noble as that may sound, Emma scoffed at the idea. Any mutant that needed protection from the lesser humans likely wasn't worth protecting. It's survival of the fittest, right? That said, Sebastian himself viewed protecting a fellow mutant as noble, and even had it as his rule that he wouldn't harm a mutant unless it would lead to his reign in his future.
Emma had to admit she saw similarities between the two of them. Both wanted a great future for mutants. Both were charismatic leaders. She understood why Azazel, Riptide, and Angel fell for Erik's tricks. And he was a very powerful mutant. Though she hated Erik for his weak mind and for killing Sebastian, she had to give credit where credit was due. Erik might someday be good for mutants. She was willing to work with him to that end. But she decided she would never like him. And she would make it abundantly clear that though she worked for Sebastian, she would only work with Erik. She would not be his flunky or pawn. She wanted the queendom Sebastian had promised her. And she intended to take it, with or without Erik.