Tbh, my gold standard for big bad wolves has become Loup Garou from Isekai Samurai, but for a RWBY Specific personal antagonist, I would consider the following:
It would be an advanced Grimm, able to disguise itself as a human like a sheep's skin. Abilities would include stuff like devastating and claw attacks and stuff like a powerful breath that can destroy buildings below brick walls, There are then honestly multiple ways that could work:
One would be a rival type: This would be the more light-hearted version, where the wolf would have developed a liking to humans and use the disguise to take part in multiple pleasures, including also being a weapons fan, similar to ruby, but disagreeing on some minor details. Their first meeting turns from beginning to gush about weapons to an "oy, what did you just say" mutual nerd-rivalry. In the grimm form, the wolf would integrate multiple weapons into the body, making it's normal grimm form far more classic, but full of equipment that give the wolf it's abilities that make it a menace in combat. Could honestly end up as a redeemable enemy, cool scenes could include ruby having a fight with the grimm form and noticing one of the weapons, which then results in a scene where she confirms her suspicion.
The other, darker variant would be that the big bad wolf is much more monstrous, downright eating people and stealing their form. It's human activity would be to secretly be a major weapons manufacturer selling trapped weapons. I would make him be the one who killed Ruby's mother, for extra angst, it devoured her in front of both Ruby and Taiyang, a fact that the Wolf also uses gleefully after remembering Ruby, in a scene that is a mix of "it was tuesday" and Ridley in the metroid manga.
Something along the line of Ruby fighting the wolf and shouting at him while he casually "who?"'s her, maybe switching his face to multiple unrelated huntresses, which drives her further into rage. She eventually does hit him, maybe with the silver eyes, which makes him go "Oh... That one. Your mother. I think she might be here... Or here...", still switching to unrelated huntresses with silver eyes two times before landing on Summers appearance, then saying something along the lines of: "Ah, here she was. Honestly, rather tough meat, that one.", maybe a bit more waffling about her culinarily.
Then I would give him an interest in eating Ruby too, in a way that makes you think of a rapist (The wolf in Perrault's version was very much intended to represent that). Lines vile enough that noone can misinterpret the wolf as anything but a completely unforgivable monster. Still in the context of eating her in the food way, but also easily readable as the other way. Ruby would escape traumatized and the wolf would be a dreaded enemy that would force team RWBY to flee, with Ruby herself having to overcome her Trauma to be able to fight the wolf, with the final confrontation ending with Ruby fighting him together with Taiyang, now able to counter him both in combat and also with words, not letting him have the fun. It would end with Ruby and Taiyang driving him to a pit of guaranteed death, from which on both a villainnous breakdown of the wolf throwing a tantrum, which Ruby now is more than able to swat aside, or it trying to get one last laugh by transforming into summer before ending itself, so Ruby and Taiyang would have to see Summer die again. Could work in multiple ways, either that does shake them up, they could also be so utterly done with it that Ruby and Taiyang have overcome the trauma to a point where they are not affected by it, Ruby could even shoot the wolf in the form of her mother, forcing it back into the wolf form. Heck, there could even be a good ending, with the people the wolf ate being resurrected again.
So, yeah, those two are what I would consider, the first one would be for a more light-hearted story, where Ruby's weapon-nerdiness could be expanded, the second one would be for a much darker story.