Death Star vs. Enterprise
Okay, it wasn't a fair comparison... in space the Death Star would have a hell of a time trying to get a bead on a warp capable ship. While the Death Star may have an advantage in sheer mass and firepower, you can't discount the Enterprise's crews ability to improvise. How many unbeatable foes have they beaten in the past?
The NCC-1701 could probably fly through the Death Star's shields and beam a couple of photon torpedoes into the station near one of the super-laser emitters. That or travel back in time and cheat.