Between Twitter, forums, and talking to people barely a day goes by where I don't witness someone saying that they're trying to break "the format," regardless of which format it is. Unfortunately I think only about 10% of the time it's being said jokingly, which is a problem. I'm going to let you in on a little secret: you're not going to break the format because you can't break the format. If you find that statement offensive then either your name is Zvi, in which case I apologize, or you're too damn sensitive.
This isn't a personal attack against you. The fact of the matter is that no one, no matter how brilliant a deck builder, is going to be breaking any formats anytime soon. Do you know how many people have "broken" a format in Magic's 17½ years? It's possible I'm missing someone but by my count it's three.
First, we should define what it means for the format to be broken which is simple. Unless a card or cards are added to the banned or restricted list, the format is not broken. Afterall, if it was broken then Wizards would fix it because that's what they do. Jund didn't break standard at any point. It was a dominant deck and it was a pain in the ass but there were still plenty of competitive decks being played in large numbers. So now that we know what we're looking for, it's history time!
The first person to break a format has no name because I have no idea who it is. To the best of my knowledge, based on both my memory and a decent amount of research, the banned and restricted list did not yet exist as of March 1994 when Antiquities was released.
If I'm correct the first person to ever look around at a room full of people wasting their time with things like creatures and proceed to say "Mox, Mox, Mox, Mox, Mox, Rack, Rack, Balance. Go." was the first person to break a Magic format. Of course, the format was broken from the start but people weren't thinking like combo players yet. Whether The Rack was printed or not yet, the 20 Mox and 4 Balance deck was absolutely the first combo deck to exist; this is fact.
Credit goes to Paul Pantera as being the second person to ever break a format. While I'm pretty confident that he's not the designer, Paul was the first person to top 8 a PTQ with Necropotence, and in fact won the tournament. This was in 1996 and since the Pro Tour existed at that point no one gets credit for anything unless they did it at PTQ or on the Pro Tour because life isn't fair. No explanation of this deck is necessary because if you're reading this then you should know about the Black Summer. And if you somehow care enough about Magic to be reading this but don't know what the Black Summer is something is seriously wrong with you. For the record, however, as much as many of you think you know about this awful time period it's a lot like the Great Depression: you can read about it all you want but unless you were there then you'll never fully appreciate how bad things were.
Finally, the most legendary player to ever break a format was Zvi Mowshowitz. Zvi was not only responsible for the famous Turbo Zvi deck, a deck that won by casting a single copy of Inspiration on the opponent about 27 times in a single turn, but I believe he is also responsible for the Tolarian Academy deck. The Academy deck was the first deck to win be consistently taking infinite turns starting on the first or second turn, and it resulted in a whole lot of banning.
Not just the Academy itself, but several pieces of the deck all the way down to the lowly Lotus Petal were banned. In fact so many cards were banned between the Academy deck and the Memory Jar deck that Wizards actually instituted an "Oops! We're sorry!" policy where you could mail them banned rares and they would mail you an equal number of booster packs (If you knew what you were doing back then you'd trade for the banned rares really cheap to get extra cheap boxes of cards. And if you really knew what you were doing you'd just stock up on cheap Academies).
You may be thinking "But, Jeebus! Those aren't the only times the format broke!" and you would be correct to say so. However, those are the times when an individual person could claim credit. And afterall, isn't the entire point of wanting to break a format to show how super awesome you are and how much smarter than everyone else you are? I mean, no one wants the format to be broken. It's boring and terrible and makes people quit the game in droves. No, this is all about bragging rights and the one other time the format broke no one got to brag. Why? Because the other time the format broke was during Mirrodin and the deck that broke the format was a preconstructed deck. If anyone threw together an affinity deck and tried to take credit for breaking Standard I will personally call them out and insert a box of Thrull tokens into their rectum.
We're (eventually) talking about deck design here and there's no pride in having Wizards build your deck for you.
Alright, history lesson over. So what do you do then? Get over yourself and stop thinking you can break Standard, Extended, or any other format. When you design trying to break a format you wind up with a pile of grotesque combo decks and inconsistent aggro decks that all win on turn one 0.0000001% of the time and auto-scoop the rest of the time.
The lesson of this story? There is no unbeatable deck and as such you will not create said unbeatable deck and become famous forever.
By all means, build and test your own decks. I do and so you should. Deck design is an important part of the game and something any competitive player should understand well and have experience in even if they've never successfully designed a "tier 1" deck. Just remember when you're building that you will not have a favourable match up against every deck in the format.
That's what the sideboard is for.