Everyone is introduced to evil at some point in their lives. Whether it is by watching the evening news or by walking into a Wal-Mart, we must all realize that the world is not perfect, that dark forces run alongside all that is good and decent, and that we are going to die alone and afraid. But for many, the first time we run into these living nightmares is in our youth, in the form of the schoolyard bully. And not even Equestria can escape from this menace.
Behold Diamond Tiara and Silver Spoon, sworn enemies of the Cutie Mark Crusaders and general jerks.
Diamond Tiara and Silver Spoon are a pair of fillies in the same class as Apple Bloom, Sweetie Belle and Scootaloo. During Cheerilee's lesson on Cutie Marks, the two quickly singled out Apple Bloom and Twist as the only ones who don't have marks, which then narrows to AB after Twist gets her Cutie Mark. During Tiara's Cutecinera, the two break away from the party to torment their target some more, only to then be confronted by Sweetie Belle and Scootaloo, thus leading to the formation of the Cutie Mark Crusaders and the humiliation of the two fillies.
After that, the two showed up from time to time to make the lives of their enemies miserable. Tiara tried to make Apple Bloom embarrassed of Granny Smith, but ended up opening herself to public humiliation while even Silver Spoon was impressed with her story. Tiara then became the editor of the Foal Free Press, abusing her position to make the entire town her personal plaything but subsequently getting reduced to printer once Cheerilee finds out. Their greatest victory, however, was getting Babs Seed to betray her cousin and join them in general bullying. But once Babs was shown the error of her ways and became part of the CMC, she responded by stabbing her former friends in the back and turning Diamond Tiara into a pig.
Diamond Tiara and Silver Spoon's names are big signs of their general status within Ponyville's academic society. They are a pair of rich, spoiled brats who enjoy putting other ponies down just for the thrill of it all. In the case of Tiara, we know her family is wealthy, as her father, Filthy Rich (har har), runs Barnyard Bargain, the Ponyville equivalent of a Wal-Mart from the way he describes it. Silver Spoon is a bit more enigmatic, as we've never seen her parents or household, but the name itself comes from the idiom “Born with a silver spoon in your mouth;” that is, she was born in a position of wealth and comfort and has never had to work hard in her life.
Of the two, Diamond Tiara is by far the bigger antagonist, even menacing the trio by herself once. She's a genuinely rotten apple with not a care for anypony but herself, her friend and her father. Much like Filthy Rich, she seems to have a business side to herself, but where he built up Barnyard Bargain over an extensive period of time using underhooved business tactics, Tiara appears to lack the patience needed for a sustainable business. Even when she was rolling high as the editor of the Foal Free Press, she never seemed to think about how humiliating her customer base would reflect on her in the long run, especially after they ran out of stories in Ponyville. She's also not above blackmail if it'll get her what she wants.
That being said, she really can't take it like she can dish it out. Whenever the shoe is on the other hoof and she's the one being embarrassed, she either shuts down or breaks into a big whine. And since this is a kid's show, this happens nearly every time she appears. She tried to humiliate AB, only to get basically shunned out of her own party. She tried to make Granny Smith (and by association, Apple Bloom) into a laughingstock, but only succeeded in revealing that her family owes their wealth to Granny's kooky jam-making practices. She tried to use the CMC to build up her paper before stabbing them in the back, but was in turn demoted and covered in printer's ink. And when she was kicking the CMC's collective blank flanks with the help of Babs, the gravy train came to a halt when she got chewed out and knocked in the mud.
Silver Spoon is a bit tougher to nail down. She's definitely Tiara's subordinate, trying to cheer her up when she's down while also taking orders. But she was also willing to applaud Granny Smith's story about the founding of Ponyville, and is much better at brushing off turned tables and the like. Still, she and Tiara are both very close, both in relationships and in the depth of their personality.
And by “depth,” I mean that if their personalities were pools of water, you could touch the bottom with your little toe. After a very confused Yakuza cut the tip off.
Fans like to give these two more of an actual character, but they're really just basic bullies. Diamond Tiara has had a few moments of aspiring for greater evil, and Silver Spoon had that one time she was fairly decent, but for the most part there's nothing else to them. They just want to make the CMC's lives miserable because it makes them look better. (Never mind that Diamond Tiara only got her Cutie Mark a short time before “Call of the Cutie,” thus implying that she was one of the few blank flank students for a while, and that Silver Spoon got hers before her best friend.) But fans want there to be more to them, so they invent things like their mothers being dead or Silver Spoon suddenly turning on Tiara or DT having a schoolyard crush on Scootaloo, simply because it gives them some character beyond the basic schoolyard bully.
But that's not what they are in the canon. They are just...jerks.
Diamond Tiara and Silver Spoon are right next to Sombra on the “Villain Complexity” list, and even he's still edging them out. The two are the most basic antagonists in the entire series to date, with only the slightest traces of an actual character to them for fans to latch onto. Sad to say, these guys simply aren't that complex, will never be complex, and are more plot devices at points than actual ponies.
So as you can guess, I don't like them very much.