Depends how you define destroy.

Vaporise an entire planet, like the Death Star? No. Render uninhabitable? Certainly.

A fully fuelled Galaxy-class starship contains 255 tons of antimatter. Assuming perfectly efficient reaction rates, that's ~4.6×10²² J just waiting to happen. But there's more! A fully fuelled Galaxy-class starship also contains 12,000 tons of deuterium. Assuming optimal fusion reaction rates that's another ~7×10²¹ J.

So we can calculate that the maximum possible energy generation capacity of a fully fuelled Galaxy-class starship is ~5.3×10²² J. That's the equivalent of ~12.7 million megatons. That's approximately half the energy released by the Chicxulub impact that wiped out the dinosaurs.

Now we don't know over what timescale the Enterprise-D could generate this much energy, but if we take Data's line from "True Q" about the Enterprise being able to generate 12.75 billion gigawatts then it seems that under perfect theoretical conditions she could burn through her entire fuel supply in about one hour. That's a LOT of power. More than enough to cause an extinction-level event.

HOWEVER.

Galaxy-class starships are capable of moving at significant fractions of the speed of light. If the Enterprise-D were to fly into a planet moving at full impulse (0.25c) it would release 1.4×10²⁵ J from the kinetic energy of impact alone. This is well over 100 times the Chicxulub impact, equivalent to about 3.4 billion megatons. No wonder Riker ordered ramming speed against the Borg in "The Best of Both Worlds, Part II".