If you want a more unique and more challenging bully/bad guy to pick. Go with Shippo. I realize it seems rather out of character at first glance, but just think about all of the other foxes that weren't influenced by Kagome and how much they liked playing tricks on everyone; and in fact had to so as a test.
He actually works perfectly if you need a bully that isn't really evil, but more like they like to have fun at other people's expense. You know the kind you run into years down the road and can't believe you're still holding a grudge and are still laughing at their own antics. If you watch Big Bang, that bully that showed up of Lenerd's is a perfect example.
If you want a really evil, but not so over done bully, you can always try that spider demon from the beginning of the series, he appeared as an old man. Sorry I don't remember his name, but he was pretty close to the beginning so it shouldn't be hard to search for him if you have the manga/show. He would make a perfect teacher that everyone hated, or principal that is way too controlling. Think Principal Kuno from Ranma, just less insane. Or even a really creepy grounds keeper. It all depends on what'cha looking for in your bully
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