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No. The point is that Sigma displays an inconsistent morality, but it doesn't seem to be Moral Myopia. Unlike Lennon, he doesn't seem to resent his father for "abandoning him". Instead, he wants justice against Grande, who killed his father for opposing the use of dark magic. However, he doesn't sympathize with the wizards, who have been fighting Grande's tyranny, and he is shocked to see Sheila and Arusu throw themselves in an attempt to save Eva, whom he considers The Load.
I'm not still sure what you're looking for? A character trope for characters who are against the Big Bad, but aren't that morally sound or heroic themselves? That would be covered by Anti-Hero. Or if you're looking for a motivation trope about somemone fighting against the bad guys for personal reasons, not for the common good, that's Not in This for Your Revolution.
What trope fits this?