So the thing about the Zimvoid variants is that they aren’t like Loki or Peter Parker’s variants where they could just be a completely different guy (or girl or alligator). They all originate from the same Zim, whose life took a turn at some point that made him distinct. Every Zim who isn’t green doesn’t come from a universe where all Irkens are orange or blue, he did something to himself that changed his skin color. Every Zim animal hybrid is a Zim who mutated himself. Carl presumably changed his name or chose it at birth.
So that has some interesting implications when we consider Number 2. He’s the best of all Zims in over 2000 universes, and taller than most Zims. Yet he still ended up with the fake mission to conquer earth, which he never completed, which is why he devoted himself to “Number 1” who promised to help him succeed and become “perfect”. He’s also the only Zim with the humility to admit to being imperfect and the only Zim who (literally) beats himself up over it rather than going into denial or deflecting blame to someone else.
I feel like these canon characteristics play well with the headcanon that he killed his Dib and the fanon of ZA2R where he secretly knows the truth and is complicit with Zib’s plans.
Like, let's assume this Zim started out like all the others, but sometime after landing on earth he finally did some honest self-reflection and worked on improving himself to become actually competent. He even got taller too, which should've done SOMETHING to elevate his esteem in Irken society. But it still wasn't enough to conquer earth and win the Tallests' favor. That's already a good starting point to explain why he's hard on himself and why he latches onto "Number 1"'s false promises. But if you add the idea that he actually got good enough to kill his Dib, but it was so traumatic he couldn't go on to conquer earth afterward (or maybe he did but the Tallest just didn't care) that would also explain why he'd be hard on himself and want to help Zib destroy all Irkens in every universe to take revenge.
