Angolul fogok írni, mert egy rohadt sznob vagyok.
Spoilers ahead! If you haven't seen Zootopia, do yourself a favor and watch it now. It's a modern epic about overcoming prejudice, stereotyping and racism. If you haven't seen Infinity War... that's alright.
Let's look at the similarities:
1. Their badasseries are sorely undercut by their unfortunate looks. Thanos' chin looks like a scrotum on a cold day and Bellweather wears her fleece in a cute bun on the top of her head.
There is a difference, though: While Thanos could at any point get plastic surgery to correct this unfortunate implication on his face, Bellweather carefully cultivates her harmless look to further her nefarious goals. Point goes to Bellweather.
2. They both have grandiose agendas for changing the world. Bellweather means to create a society wherein prey rule over predators, under her rule, and Thanos is an eco-terrorist who wants to kill every odd person to lessen ecological load on the universe.
I have to side with Bellweather on this one. Her goals are much more in alignment with her life experience of being bullied by the predatory Mayor, a lion. Her goal, while ill conceived, is as sympathetic as any villain's evil plan can get.
Meanwhile Thanos openly admits that his lofty ideals rise out of spite: he got the idea of murdering half the population of his planet rudely rejected in the past, and now to soothe his hurt ego he wants to do the same on a galactic level. It's almost like he has his goal set (mass genocide) and works his way back to an idealistic shrinkwrap with a ribbon around it.
(And that is ignoring the part where collecting all those stones could solve the alleged ecological crisis by simply creating more resources and zero murders.)
Another point goes to Bellweather.
3. Sweet tooth for the good guys. Thanos has a hardon for Gamora, calling here endearing names like "little one" while dearly wishing his metal pants had more spare room at the front. Bellweather has sweet platonic lesbian love for Judy, going so far as helping her investigation and using her rise to fame, even if it leads to her eventual arrest.
I have to say it clear: I don't get Thanos' emotion. It is not built up, it feels like an artificial sweetener to make an otherwise irredeemable psychopath seem like an interesting character. Thanos has no reason to even like Gamora, other than her smokin' hot looks of course. Thanos supposedly hates betrayal, yet from the get-go Gamora makes it crystal clear that she hates Thanos and mildly disagrees with his goals. It should come as no surprise that she gets thrown into an abyss. That entire scene feels so forced and artificial, I'm still cringing when I remember it.
Filmmakers, please note: you cannot create depth to a character by this sort of backtracking. Omnicidal maniacs don't suddenly become interesting and layered individuals just because they care about someone for a four-minute scene in a 150-minute movie about mass murder. Thanos could go and listen to the New York Philharmonics play Beethoven and not become more than a base psychopath. He could PLAY Beethoven with the New York Philharmonics for all I care. (Unless he turns maniac because of Beethoven. That could be interesting.)
On the other hand, Bellweather feels genuine kinship to Judy. They are both in a profession dominated by predators (politics for her, and police for Judy). She's got real reason to think of Judy as her daughter, where Thanos would not know how to relate to a daughter is he stepped on one.
Another big point for Bellweather.
4. Evil gloating. Let's face it: when you made a good ol' dastardly plan and are about to succeed, it's fun to rub it in the hero's face. No James Bond villain can resist the temptation! However, there is a secret rule: you have to hold off on the gloating until after your victory is ensured.
Thanos is very clear about his goals right from the start. His evil plan is no secret. He could take out full page ads on every major newspaper on every planet and not make his endgame better known. It's a mystery why he has underlings helping him, knowing full well that doing so is carries a 50% chance of destruction, assuming no earlier death by hero, punishment for failure, or other minion hazards.
Bellweather tones down the evil gloating a lot. In fact, she is hiding in plain sight, waiting until the very end to reveal her plan, and it becomes her undoing. Thanos can get away with it on virtue of being a physical god that none of the heroes have any chance of defeating, but Bellweather should have observed Evil Overlord rule #6.
Point goes to Thanos.
5. Goal oriented villainy. Thanos travels the universe, merrily murdering, torturing and mind playing his way into collecting infinity stones. Meanwhile, Bellweather engineers the outbreak of predators going savage in order to play off of racial tensions between predators and prey. They both have their work cut out for them.
Of course, Thanos has no real plan other than the trusty old scheme of "beat up everyone and torture heroes' loved ones for info". He could never have never hoped to win, if he was not assisted on all sides by the heroes' utter stupidity at every turn. Bellweather, on the other hand, single-handedly masterminds a massive conspiracy, manipulating the mayor, the police and the press on a formidable scale. True, her plan does include Judy becoming a star policebunny, but it's not the core of her plot and the rest could be pulled off without the protagonist's assistance.
Point goes to Bellweather.
Final tally: Bellweather wins 4 to 1.