This are the list of achievements and this list will help you a lot how to obtain them
Cheat mode:
Hold L + R and press Down, X, Up, Y, Down, Down, Up, Up (at the main menu). Release L + R
and a "Cheat" option will appear at the main menu. Select the "Cheat" option,
Then enter one of the following case-sensitive codes to activate the corresponding
cheat function.
God mode:
Enter 8wonder as a code.
Level select:
Enter KKst0ry as a code. Note: This code includes the number "0".
One-hit kills:
Enter GrosBras as a code.
999 ammunition:
Enter KK 999 mun as a code.
Bonuses completed:
Enter KKmuseum as a code.
Unlimited spears:
Enter lance 1nf as a code. Note: This code includes the number "1" in the second word.
Machine gun:
Enter KKcapone as a code.
Revolver:
Enter KKtigun as a code.
Shotgun:
Enter KKsh0tgun as a code. Note: This code includes the number "0".
Sniper rifle:
Enter KKsn1per as a code. Note: This code includes the number "1".