Here is the full list of all 12 Resident Evil 4 achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Clear the game on the highest difficulty.
Summon the master of the lake. Don't rock the boat.
Acquire all of the costumes in the game.
Defeat Krauser, your former partner, in battle.
Defeat Saddler in battle, and escape from the nightmare.
Acquire all of the bottle caps in the game.
Defeat Salazar, and make your escape from the castle.
Turn the tables on Verdugo, the right hand of Salazar.
Defeat the village chief in battle.
Rescue the president's daughter, Ashley. Afterwards, the real fun begins.
Outmaneuver the rampaging beast, El Gigante.
Ring the mysterious bell. What happens after that, is up to you.