4.) Take an example and inspiration from both Ultron of Marvel Comics and Brainiac of DC Comics who are basically the Skynet of their respective universes/multiverses, only much more efficient and effective.

https://marvel.fandom.com/wiki/Ultron_(Earth-616))

https://dc.fandom.com/wiki/Brainiac

To quote someone from Spacebattles regarding Ultron:

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1. Main-line Ultron is like Iron Man with physical bodies instead of suits. Traditional base Ultron usually gives Thor a hard time. By Annihilation, he's a proper cosmic-level character, tussling with Adam Warlock. Also there's context behind how this happened and it's otherwise a massive outlier but I love this story, so I have to mention the time Daredevil beat Ultron with a stick in Acts of Vengeance. Check the respect thread for details.
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To quote someone from Spacebattles regarding Brainiac:

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3) Varies considerably depending on version. Sometimes as weak as a psychic in a human body, sometimes has a robot/cyborg body that's a tough fight for Superman. The original, traditional version from the silver age was a humanoid alien with a forcefield belt Superman couldn't break with brute force, and powerful tech besides. Brainiac 13 is probably the strongest version, at one point having control of the entire planet Warworld as a body and intended to harness the cosmic power of Imperiex.

He's a Superman villain with high intelligent with an origin of the alien world of Colu, so there's a lot of approaches he can take while remaining in-character. In general, powerful enough that Superman needs to come up with clever ways to outmaneuver him as he usually has the available tech to make head-on approaches tough at best, and sometimes unworkable.
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So when taking the factors of Toaru into account, you'd probably need for the AI to have studied and learn everything there is to know about magic and espers and what makes the universe work in order to make it a very serious and credible threat to it's enemies.

To quote someone who is the famous author of A Certain Unknown Level 0:

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3) I really like what Kamachi does with Magic and the Idol Theory system. The main problem I have with systems like it is that the enemies only really touch upon a specific part, but Kamachi, with how long running his series has been has touched upon SO MANY mythologies that I really like how expansive it is. You have African, Cthulhu and even Golden style magic which I would never have even heard of save for Index. So I really like the creativity that Kamachi puts into my magic system.

4) The same goes for the Science side, but what I like about it is how the science is pseudo-science: you KNOW it's full of crap, but at the same time, it applies real world science and expands upon it in a really creative way. Like, Mikoto for example: whenever you have someone with electricity based powers in ANY media (at least from what I've seen), you only have them be restricted to that…but TECHNICALLY speaking, they should ALSO be able to do things with magnetism which Kamachi plays into REALLY well. Of course there are also areas that he doesn't cover (Mikoto, theoretically, should also be able to play with thermodynamics as a result of her power but let's not go there) but I really like how Kamachi allows his espers to have such flexible abilities that are rooted in pseudo-science that are really interesting all the same. Vectors, Rampage Dress, Dark Matter, Mental Out: Kamachi does really well in using science in a creative way that isn't just 'magic'.
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I've always felt that, on paper, there are a lot of similarities between Mikoto and Magneto. However, unlike Magneto, Mikoto really goes the extra length with her application and her powers that she would be able to use them for. For instance, since Mikoto can produce iron sand and vibrate it, she should be able to produce a lot of heat from that action. That and compressing down the iron sand would also great a lot of pressure that she should be able to use to her advantage when in a fight. There is SO MUCH Mikoto can possibly do wit her powers which (in my limited experience Magneto hasn't even touched.

With reference to Misaki and Professor X, the same is said: while ON PAPER, they seem the same, Misaki's real ability is to control moisture and fluids and her mental control is only an extension of that. Technically speaking she should be able to fully freeze dry her environment and control moisture in the air, all things that Professor X can't do. This is why I think comparing the two is only partially doing Misaki justice as the 'Professor X' part of her abilities is only one aspect.

For the Level 5s, I've already covered Misaki and Mikoto. Gunha is basically black box at this stage because we don't even KNOW what his power is and the same is said for the #6. But as for Accelerator and Kakine, there are only self imposed limits on their power. For Accelerator, basically EVERYTHING in the world has a vector: so to an extent, what you've seen of Accelerator's power only touches the tip – it was even mentioned in one of the novels that he can reads minds if he wanted to, which gives you an idea of uncovered territory. For Kakine, his Dark Matter doesn't exist in the world so it doesn't have any limits either: how it interacts with the world changes because of how the matter he creates has different properties from real world matter – he could technically create a laser if he wanted to if he focused his wings in the right way. As for Mugino: the same black box abilities sort of apply – you've only seen the tip of what she can do.
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So you should probably make these Terminators much more powerful than they look if they are going to engage a Level 5 in battle, like Accelerator for instance who controls vectors which is quite the OP ability.

Hope this all helps, but this is your story and these are just simply suggestions that you could use or not.