A few other answers have suggested dropping a black hole into the Sun. This would trivially certainly destroy the Sun by consuming it, but there's another, much more spectacular, mechanism at play. And that is accretion.
When matter falls into a black hole, it won't fall straight in unless aimed incredibly precisely. Instead, an object dropped into a black hole will more often be shredded by the black hole's tidal forces, then form into a disk of gas orbiting the black hole. The gas's angular momentum keeps it from falling inward right away, but it can bleed off that angular momentum by knocking into particles orbiting just a bit farther outward, transferring momentum and letting the inner edge of the disk creep ever closer to the event horizon. This whole turbulent momentum-exchange process produces heat- a lot of heat. There's a lot of potential energy stored in a mass suspended above a black hole, after all, and when the mass falls in, that energy has to go somewhere. In fact, an accretion disk can covert around 10% to over 40% of the mass of the infalling matter into energy that can radiate away from the hole- far more than the 0.7% attainable by nuclear fusion.
Imagine that- a weapon capable of converting 10% of the sun's mass into energy. If Jupiter's mass-energy is comparable to a supernova, then 10% of the sun's... is just insane.
Now, there are a few caveats here. For one thing, it's not instantaneous. Black holes can only consume matter at a certain rate. The accretion disk emits radiation, and that radiation exerts a force on any matter that it hits, pushing it away. When that force equals the force of gravity pulling matter inward, they balance out- and the hole can't eat any faster. Some matter will continue to slip in, as that's powers the radiation pressure; but the rest of the star will be kept out. This is called the Eddington limit. It increases linearly with the mass of the black hole, which means that bigger black holes can eat faster. And since black holes grow by eating, a black hole dropped into a star will grow exponentially until there's nothing left for it to consume.
So you could kick-start the process by using a large black hole, or use a small black hole and let it act as a sort of apocalyptic time bomb. Over time, the star would grow brighter, larger, and redder as the black hole outstrips the thermonuclear reaction in its core (which will happen around when the hole has absorbed about 0.1% of the star's mass), until the rate at which the hole's consuming matter exceeds the rate at which that matter can heat up and expand, whereupon the star will become smaller, hotter, and ever more luminous until there's nothing left to shield the rest of the solar system from being scoured clean by the incredibly intense radiation from the accretion disk.
And I have absolutely no idea over what sort of time scale this would take place. I've made a couple of attempts at the math, but I'm fairly sure I messed it up somewhere.
Another caveat is that much of that radiation may be directed directly out of the plane of the solar system. We might wind up essentially creating a gamma-ray burst. Sometimes, when massive stars collapse into black holes, much of the energy of the supernova is directed into two narrow beams of gamma rays perpendicular to the accretion disk. The same thing might happen when a black hole fully consumes a smaller star, depending on how quickly the star is spinning.
The third caveat is that this won't fully vaporize the solar system- there will for sure be a stellar-mass black hole left behind, and perhaps also some planets. I have no idea whether or not they could survive this kind of event, although their biospheres almost certainly wouldn't. And if the biospheres somehow did survive the blast, there would be no sun afterwards, and the planets would freeze.