And, at least in the Trek-verse, there are some planet-killers. The Doomsday Machine, for example- with an anti-proton beam capable of cutting up planets- which the Enterprise survives being hit with.
Similarly, the shields of the Enterprise shrug off a hit from a nuclear weapon in Patterns of Force- as far as I can tell, proton torpedoes in Star Wars are comparable to nuclear weapons.
I think there are some scenes in TNG where phaser fire bores a long way into the crust of a planet.
Trek ships are small, but they are quite heavily shielded, and possibly quite well armed as well- in A Piece of the Action, Kirk targets a city block from orbit with phaser fire- which shows some accuracy.