Also, remember. Doom went out of his way to create something to kill that which couldn't be killed. Something that existed in a positive manner that was thought invulnerable. He went out to find a way to kill it. Not to detain it. To kill it. To introduce something into the world that would make something immortal mortal.
That's like some Satan killing Angels shit. Toons in that universe will never be the same because someone found a way to kill them even after his death.
Doom's a close second for me. I admit I haven't got a lot of reasons to put him down beyond the fact that Doom appears in what I'd call a more cynical movie, meaning that the audience watching it is better equipped to handle this snarling evil than Man, whose 'appearances' in Bambi take a movie from being the safest and most friendly looking Disney movie of all to one of literal animal terror. Just look at the difference in Flower and The Hounds. It's a really stark contrast in a movie that's aimed at little kids. When Man shows up the first time, the animals go from being sort of detailed cartoon animals to colorful blurs moving as fast as they can to get away from him.
Even the characters in Roger Rabbit are better at handling Doom than the animals in Bambi at handling Man. Like, Eddy hates and probably fears him, but he faces him with jokes and wit, while the animals are driven insane by the simple presence of Man. There are words to explain and communicate who and what Doom is, what his goals are, his motives, his personality. There isn't any of that for Man. Man is only ever explained in terms of fear. Bambi doesn't even ask
who they ran from or
what they ran from. He asks
why they ran, and Bambi's mom doesn't explain that they ran from an apex predator who kills and eats everything it can, she says "Because
Man was in the forest." and that's it.
Honestly I was just really captivated by the force of Disney's point with Man in the movie. It's more like a monster from a horror-thriller than your standard Disney villain. Man doesn't have a song. He doesn't give a speech while he strokes his beard. He doesn't gloat, pose, or do most anything that the standard Disney villain does. Yet he's infinitely more menacing than any of them. Comparatively he outclasses all of them. The damage he inflicts upon Bambi and his family and friends far outstrips anything that any other villain in any other movie does.
And the fact that Man might not care at all, and that all this pain and devastation might mean
nothing to Man is a powerful message. The ease and leisure with which Man inflicts all of this upon the cast of the film is perhaps the main point. Other villains have to go out of their way to do bad things, but Man does bad things because he doesn't go out of his way to do good. Every other villain has some motive. Hell, even Chernabog's simple "I am evil embodied" is more motivation than you see Man having in the movie. To the animals he's an antagonist beyond the natural, and the source of much of their sadness and pain.
Add to it that, again, Bambi is otherwise an entirely innocent movie about growing up in the woods and it makes just how fucking terrifying Man is stand out that much more. Throw in the very specific fact that he kills Bambi's mom and that
that is the moment everybody remembers about the movie and what that moment is famous for doing to children and Man-as-the-villain is really hard to resist because it's just so striking.
Like someone else said in the thread: we're used to Man vs Nature, but Bambi is actually Nature vs Man, with the decidedly heavy slant of "Man way outclasses Nature" and the movie takes on a whole new light to me.