If you're going to have your bad guy do something despicably evil by destroying something huge, make it something that the PCs care about. Something they've fought for and made sacrifices to save.

Something they've actually heard of before.

Transcript

Darth Vader: Goodbye, my love.
{The Peace Moon laser hits Naboo and the planet blows up}
[SFX]: KABOOOOMM!!!!
{Leia, Luke, Han, Obi-Wan, and C-3PO in shocked silence}
R2-D2: You. Utter. Frakking. Bastard.