Major spoilers ahead for Episode 9 of Agents of S.H.I.E.L.D. Season 5, "Best Laid Plans."
The fifth season of Agents of S.H.I.E.L.D. saw the action moved 74 years into the future. By the time the agents arrived in 2091, the Earth had been destroyed, the remnants of humanity were stuck almost entirely on the Lighthouse, and the Kree were in control of almost everything. One of the biggest questions of the season so far has been how exactly the Earth could have been destroyed. According to the surviving humans, Daisy more or less quaked the planet apart by just using her powers, but S.H.I.E.L.D. fans (and Daisy herself) know that she's nowhere near powerful enough to destroy a whole planet all on her own. Now, "Best Laid Plans" may have confirmed how Earth really was destroyed: gravitonium.
Okay, gravitonium and Daisy. Agents of S.H.I.E.L.D. hasn't ruled out Daisy having some sort of role in Earth being blasted apart, and the video footage from a previous episode indicates that Daisy may have contributed to the quakes that tore the planet apart. Nevertheless, Daisy never would have been capable of such global damage if not for an element that had already destabilized the planet, and that destabilization is almost certainly due to gravitonium.
Gravitonium is a rare element in the Marvel universe that was introduced on Agents of S.H.I.E.L.D. back in Season 1. The element distorts the force of gravity within itself and, when stimulated by an electrical current, it can cause powerful and uncontrollable gravity waves. The waves can affect the gravity of anything within range, and we saw its potential devastation in Season 1. It was never established how gravitonium might react if exposed to powers like Daisy's as opposed to electrical current, but it stands to reason that the effect would be at least equally devastating. Gravitonium combined with Daisy's powers as Quake could conceivably result in destruction on the scale of Earth breaking apart.
"Best Laid Plans" was the second episode of Season 5 to feature gravitonium. Fitz and Simmons discovered a sample of gravitonium on board the upgraded Zephyr when they were attempting to get it ready to fly again, and they were both somewhat aghast that such a dangerous element was just tucked away in the wall of a ship. Good old Fitz had drawn up the plans for a Zephyr upgraded with gravitonium, but never imagined that such changes would ever actually be made. Fitzsimmons realized that the gravitonium on the Zephyr must be responsible for keeping the remnants of Earth intact, just as the gravitonium on the Lighthouse was enabling the Kree to maintain an artificial gravity there.
The appearance of two different samples of gravitonium -- which was so rare that some scientists believed it didn't even exist prior to Season 1 -- could point toward the discovery (or manufacturing) of a dangerous amount of gravitonium. If a large enough supply of gravitonium is in the wrong place at the wrong time and Daisy uses her abilities, the planet could theoretically be ripped apart and destroyed to the extent that it has been by 2091. Daisy would technically have contributed to the destruction of the world if this is the case, but it wouldn't qualify her as "Destroyer of Worlds." If anything, the fault might lie with scientific minds who were messing with elements they shouldn't have.
We'll have to wait and see. Agents of S.H.I.E.L.D. didn't 100% settle whether or not gravitonium is what caused the destruction of the Earth, but we can be confident that gravitonium will have a part to play in the rest of the current arc. Surely S.H.I.E.L.D. wouldn't have brought an element not mentioned since Season 1 back twice if it wasn't going to be a big deal! We can only hope that none of the good guys die before the arc is completed.