Here is the full list of all 49 Trepang2 achievements.
Collect all intel docs
Acquire all weapon parts
Complete all campaign and side missions on Very Hard difficulty or higher
Eviscerate Dr. Emerson’s corpse
Kill all TF27 soldiers in Site 14
Throw a TF27 soldier into the helicopter blades in Site 14
Throw an enemy into the vent in the first combat encounter in Site 14
Stealth kill an entire squad without anyone becoming alerted
Kill an enemy with a flashbang impact
Kill an enemy with a tomahawk
Use every bullet in a pistol magazine to get headshot kills
Complete Level: Site 83
106 is reborn
Let the world know
Break The Cycle
Cycle 106 comes to an end
Completed Level: Horizon HQ
Kill the Horizon CEO
Complete Level: Kellington Colliery
Kill an enemy by shooting through his helmet with a DMR
Complete Level: Jorvik Castle
Kill the Patriarch
Acquire the dual wield serum
Destroy 1000 cultist books
Complete Level: Site 32
Complete Level: Oil Rig
Shoot an enemy while he’s thrown as a hostage grenade, detonating his grenade
Complete Level: Crash Site
Complete all campaign and side missions on Hard difficulty or higher
Complete Level: Gunnarson Complex
Grab an enemy, throw and kill him with a headshot
Complete Level: Pandora Institute
Kill the Mothman
Collect the Syndicate coin “XCV”
Complete Level: Iron Dragon Data Center
Alert an enemy by shining a flashlight from behind, shoot him before he turns around
Shoot an enemy’s thrown grenade, killing him with it
Kill an enemy with a headshot on final bullet in the mag
Kill a heavy soldier
Escape from Site 14
Kill 3 enemies with 1 grenade
Slide into an enemy and grab him while he’s ragdolled
Collect 50% of all intel docs
Execute your first hostage
Collect the Syndicate coin “CV”
Use a weapon bench to customize a weapon for the first time
Destroy 100 beer/wine bottles
Complete all campaign and side missions on Extreme difficulty or higher
Complete all campaign and side missions on Rage Mode difficulty