Per title. This kind of deck would acknowledge that its mainboard plan is not very strong, but expect that its sideboard is powerful enough to tilt games 2 & 3 in its favor. Or, phrased differently, has there ever been a deck whose mainboard plan is not very good, but whose sideboard plan is strong enough to compensate?
I'm not aware of any such deck. The two closest are:
- The traditional midrange deck like Jund expects to improve against all strategies post-board since it has the tools to beat everything in its 75. However, even this kind of deck hopes to win game 1; it usually has versatile cards maindeck that can disrupt whatever it faces, and there are matchups where it is naturally advantaged.
- I once conceived of a deck that would play every good card legal in the format, with something like 400 cards maindeck, then after sideboard it would board down to the specific 60 cards most effective against the opponent. Such a deck would indeed expect to lose game 1 and win games 2 & 3. However, this idea is illegal, because sideboards cannot have more than 15 cards even postboard.
I do know of decks that do the reverse - they expect to win game 1, then hope to win one of games 2 and 3. Examples would be graveyard and artifact decks. Game 1 they are devastatingly effective, but post-board they can expect opponent to have strong sideboard bullets, which makes the games much harder. Still, if they can steal one of the postboard games, they still win 2-1.