ACHIEVEMENT - HOW TO UNLOCK
First Blood! (5 points) - Kill a special enemy.
"Twentieth" Blood! (10 points) - Kill 20 special enemies.
No Mercy! (10 points) - Perform 20 Finishers.
I'm Just Getting Started... (10 points) - Kill 1000 enemies.
It's over 9000!!! (25 points) - What! 9000 (kills)? There's no way that can be right! Can it?
First Action Hero (10 points) - Defeat an enemy hero.
Practice Makes Perfect (15 points) - Perform 100 Perfectly-Timed Attacks on enemies.
Now That's Just Mean... (5 points) - Kill 10 fleeing enemies by throwing picked-up weapons.
No Vacancy (25 points) - Complete a chapter with enough items equipped to completely fill the largest item grid.
I Like Choreography (25 points) - Perform 3 different Finishers with each hero.
A Lot of Blood (10 points) - Kill 50 enemies while in Fury.
A Perfect Amount of Blood (25 points) - Kill 496 enemies while in Fury.
Denied! (10 points) - Perform a parry on an enemy's parry in a duel.
I Love Items! (5 points) - Buy 10 items.
There's No Escape! (5 points) - Kill a fleeing enemy by throwing a picked-up weapon.
They See Me Rollin', They Hatin' (10 points) - Perform a rolling Quick Attack on an enemy from behind.
That Wasn't Too Hard... (50 points) - Complete the game on Hard or Expert difficulty.
I'm Really Good at Action Games. (70 points) - Complete the game on Expert difficulty.
Perfect! (10 points) - Perform a 6-hit combo of Perfectly-Timed Quick Attacks on enemies.
Without a Scratch (30 points) - Complete a chapter without being damaged on Hard or Expert difficulty.
Are You Tough Enough? (30 points) - Complete a chapter without equipping any items on Hard or Expert difficulty.
Gordie Howe Hat Trick (5 points) - Complete the Arena, Rampage and Bloodlust challenges.
Time Extension! (15 points) - Maintain your Kleos for 3 minutes during a chapter.
Bless You (15 points) - Collect a Blessing.
A Lot of Time on Your Hands (55 points) - Complete all secondary objectives on any difficulty.
Items Make Games Awesome (75 points) - Buy all of the items.
Here Comes A New Challenger (5 points) - Reach Hektor in the Epic Bloodlust challenge within 10 minutes.
Epic Success (30 points) - Complete the Epic Arena, Epic Rampage and Epic Bloodlust challenges.
Life is a Blessing (25 points) - Collect all Blessings in a chapter.
The Underdog (15 points) - Win a duel after entering it with critical health.
By the Gods! (25 points) - Kill 500 Trojans in Plague on Expert difficulty.
10-Second Knockout (10 points) - Defeat an enemy hero in under 10 seconds.
Efficient Killer (5 points) - Perform a Finisher on each of the 6 special enemy types.
Too Fast to Furious (10 points) - Completely fill the maximum fury meter in under 2 minutes without using items that generate fury.
Cry Me a River! (25 points) - Escape Skamandros.
Knock, Knock! (25 points) - Open the gates of Troy for the Greek army.
Farewell, Troy... (50 points) - Complete the game on any difficulty.
From Paris with Honor (25 points) - Defeat Menelaos in a duel for the hand of Helen.
Where Is Your God Now? (25 points) - Bring down the statue of Apollo.
I'm Too Old for This Shi...p. (25 points) - Escort Agamemnon to the Greek ships.
Miss Kleos (15 points) - Achieve 350 Kleos with Penthesilea during a chapter.
Face That Launched 1000 Ships (55 points) - Unlock all of Helen's concept art.
Stop with the Sibling Rivalry! (3 points) - Do not attack Hippolyte when she comes to haunt you.
Zombie Homicider (3 points) - Perform a Finisher on an enemy zombie.
What a Waste... (2 points) - Miss all of your attacks while in fury.
Epic Failanx (2 points) - Break the shields of everyone in a phalanx without killing any of them.
This Is a Non-Smoking Section (15 points) - Get 3 enemy zombies hit simultaneously by Lyssa's ground smoke attack.
Getting Kicked Down There... (15 points) - Get 5 enemy zombies kicked by the statue of Apollo.
7 of Clubs (15 points) - Get 7 enemy soldiers killed by the Cyclops.
Hard Target (15 points) - Defeat the Griffin without getting hit by any sand pillar attacks. 

Unlock the listed effects by completing the game under the corresponding difficulty settings:

EFFECT - DIFFICULTY
Super strength - Easy
Big head mode - Normal
Dead with one hit with double money - Hard
Unlimited ammunition - Expert