Here is the full list of all 19 Obscure II Obscure: The Aftermath achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Obtain every available weapon during a game.
Open all of the chests.
Finish the game.
Jedidiah won't make any more trouble.
Prepare a serum, an improved serum and a powerful serum.
Get to the main yard at Leafmore.
Find Sven.
Consume 10 energy drinks.
Get to Jedidiah's house.
Find Amy at the Fallcreek dam.
Heal a teammate 10 times.
Go through the hospital.
Recharge electric weapons 10 times.
Find Jun.
Find Corey's car and get to the hospital.
Meet up with Kenny and Amy at the Delta Theta Gamma party
Go to the Delta Theta Gamma party.
Open a chest.
Over-consumption of tea is not recommended.