I especially like the part where it's revealed that Khan Noonien Singh escaped from the Reliant at the last second in a shuttle, went to warp, then went to a Denobulan planet to have himself rejuvenated. The way they did that whole thing as a flashback was really well done. Then when he gets in the fist-fight with the Kirk clone, wow ... what action. They could have left out the part where Captain Sisko comes out of the wormhole to repair spacetime, it was sort of too deus ex machina for me.
For anybody who hasn't seen the movie (and who hasn't already guessed the following), yeah, I made all that up.