Total number of achievements 30:

Rookie Life:
Difficulty: Easy
Requirements: Go through the tutorial, but before completing it, get killed by the Imp in the last room.

Just Getting Started:
Difficulty: Easy
Requirements: Complete chapter 1 on Normal. This can be done in single player or co-op.

Take it Back to the Carpet:
Difficulty: Easy
Requirements: Talk to Gregin in the lobby and select the 're-spec character' option.

Gregin's Mighty Toucht:
Difficulty: Easy
Requirements: Talk to Gregin in the lobby and select select the option to modify your character. One of the sub options will be to switch gender.

Now That's a Nice Chest!:
Difficulty: Easy
Requirements: There is a %2 chance that a chest spawn when entering an area. Open one of these chests to get the achievement. When one of these chests spawn, you will be notified via a new 'hint'. The chests seem to only spawn in wilderness areas and not inside towns/villages/castles.

Companionship:
Difficulty: Easy (if you have friends that play) Medium(if you rely on strangers)
Requirements: Complete a chapter with 2 non-AI players. Create a public or private game (or join one hosted by another player), and then complete any chapter. I do not know if this achievement can be unlocked when you have 3-4 players in the group.

More the Merrier:
Difficulty: Easy (if you have friends that play) Medium(if you rely on strangers)
Requirements: Complete a chapter with either 3 or 4 non-AI players. Create a public or private game (or join one hosted by another player), and then complete any chapter when you have 3 or 4 players in your group.

!:
Difficulty: Easy
Requirements: Complete any side quest. The easiest & quickest one to complete is finding and returning the lost boy (Marty) in chapter 2. The boys mother can be found in the Castle town, (west and north of the inn exit). The boy can be found In the forest (go left when there is a fork, if you fight bandits you when the wrong way). Simply talk to his mom to start the quest, walk to the forest to talk to the boy, and then journey back to the castle to speak with the mother again (protecting the boy along the way).

Hasta la Vista, Baby:
Difficulty: Medium
Requirements: Complete any challenge. The easiest two challenges to complete are the escape from the collapsing cave (end of chapter 3) after fighting the vine boss and the challenge where you need to dodge bombs thrown by Barbuda on the bridge at the start of chapter 4.

AAAARrrrrRRggGGGhhhHHH!!!:
Difficulty: Medium
Requirements: Use a soul charge. Fill up the circle in the upper right hand corner of the screen. When it is full, use your soul charge (actual button press depends on your hotkey config. for elementalists, bring up the spell select wheel and connect all runes). When your party dies you lose all of your accumulated soul charge progress.

Bedazzled!:
Difficulty: Medium
Requirements: Augment an item. To do this, first find a gem and either a helmet, armor, or weapon item. From your inventory select the gem and its augment option, then select the gear you want to use it with.

Don't Feed the Slime:
Difficulty: Medium
Requirements: Fully feed a Blood Slime. To do this, let a Blood Slime hit you until it is at full power.

Took the Blue Pill:
Difficulty: Medium (easy if you find someone to rush you in multi-player. hard if playing solo)
Requirements: Beat Chapter 10 on Normal difficulty. (may unlock if you do not have it and beat it on either hard or epic)

Almost a Hero:
Difficulty: Hard
Requirements: Beat Chapter 10 on Hard difficulty. (may unlock if you do not have it and beat it on epic)

This Story is Happy End:
Difficulty: Hard
Requirements: Beat Chapter 10 on epic difficulty.

Valandrian Horders:
Difficulty: medium (time consuming)
Requirements: Collect and hold 99 of any 1 material.

Gamblin' Ramblin' Man:
Difficulty: medium
Requirements: Complete 5 levels of crawl and then select to roll the slot machine as your reward.

Chicken!:
Difficulty: medium
Requirements: Complete 5 levels of crawl and then select the blue chest as your reward.

Wild Sergey Appears!:
Difficulty: medium
Requirements: Have the slot machine roll three music notes in the reward room for the crawl. You should get the achievement before proceeding to the next level.

WINNING!:
Difficulty: hard
Requirements: Open the orange chest in the crawl. To do this, the slot machine has to roll the result to unlock it.

Bloody Injustice:
Difficulty: hard
Requirements: Defeat a Blood Golem in the crawl. To do this, the slot machine must roll to roll the Blood Golem encounter.

Jelly Shots:
Difficulty: hard
Requirements: Beat the secret boss in chapter 2 on epic difficulty.

Davey Would be Proud:
Difficulty: hard
Requirements: Beat the Kraken secret boss on Epic difficulty. The boss is at the start of chapter 9, but you need to retrieve the telescope from chapter 8 to access it.

The Wolf Pack:
Difficulty: hard
Requirements: Beat the chapter 6 secret boss on epic difficulty.

Smells Fishy:
Difficulty: hard
Requirements: Beat the chapter 5 secret boss on epic difficulty. To unlock this boss you must complete the chapter 2 side quest and continue until you get to chapter 5. Otherwise the side quest that opens the sewers will not be accessible.

Can't Touch This!:
Difficulty: hard
Requirements: Complete chap 10 on epic without getting hit. (blocks/counters are not allowed)

Now That's a Knife!:
Difficulty: hard
Requirements: equip a legendary weapon. The weapon you need to equip is purple and named Requiem. The recipe is dropped from chap10 epic boss.

Chain Gang:
Difficulty: hard
Requirements: equip a complete set of legendary weapons. (1 orange or purple item in each of the 5 slots)

DING!:
Difficulty: hard
Requirements: 100% every chapter. You need to do this on each of the three difficulties.

Die Hard:
Difficulty: hard
Requirements: complete all 10 chapters without returning to the lobby.