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I wish we got to see more of Rei's feisty side. It's clearly there in the TV series, we know this from Rei 1, Unit-00's anger management issues, and Dummy Plug Eva-01. If you stretch it, there's also her attitude in Episode 26's alternate reality. Everybody else acts reasonably in-character, but Rei experiences a massive shift in personality, likely due to never having to experience traumatic soul diffusion or bitches who choke her out for making a snarky remark as a kid.
If you want to go further than that, there's always EoE where she's incapable of showing a friendly face to Shinji. But that's kinda mean so I don't want to.
Even in the simplified Rebuilds, they retained Unit-00's rampage for 1.11 and they didn't say what personality the Dummy Plug is loaded with in 2.22, so it could've still been her. There's a substantial amount of material they could have worked with that could have fleshed out her character in a whole new way.
