Here is the full list of all 251 ORION: Prelude achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Complete 50 Mission Objectives
Kill a T-Rex by yourself
Reach Level 5
Activate a Dinosaur Skin in the 'Loadout'
Kill 100 dinosaurs
Complete 25 Mission Objectives
Kill 50 dinosaurs
Complete 10 Mission Objectives
Reach Level 1
Kill 25 dinosaurs
Win a game with a Developer or someone who already has this achievement
Win a match on Depth
Win a match on Covan
Win a match on Eden
Get a kill with every weapon
Get eaten by a T-Rex
Kill 250 dinosaurs
Kill 500 dinosaurs
Kill 1000 dinosaurs
Kill 10,000 dinosaurs
Kill 25,000 dinosaurs
kill 50,000 dinosaurs
Spend 5 hours Jetpacking
Spend 1 hour cloaked
Spend 1 hour healing
Punch a T-Rex, Raptor and Rham to death
Turn on 50 generators
Heal 50 Generators back to 100% health
Run over 1,000 Raptors
Spend 10 hours in vehicles
Spend 100,000 Credits
Spend 1,000,000 Credits
Spend 5,000,000 Credits
Spend 10,000,000 Credits
Complete a map on hard mode
Take 5,000 damage in a single life
Kill three raptors with one grenade
Roll out of a T-Rex chomp
Kill a dinosaur with every vehicle
Drive a vehicle full of buddies to their deaths
Kill 100 dinosaurs without dying
Kill a developer or someone who has killed a developer
Start at wave 1, win, and spend less than 5,000 Credits
Earn 200 assists in a single match
Find a hidden vehicle
Top the scoreboard 10 times on teams of 4 or more players and win the round
Ride a dino for 10 seconds
Kill the first and last dino in a wave
Reach the top of the world
Be 1,000 meters from the current base during a wave
Kill 1 or less dinos in 3 consecutive waves
Stomp 100 Raptors in the Cobra Mech
Punch 100 dinosaurs to death
Get picked up 1,000 times
Punch a dinosaur to death when you have 10 or less health
Punch a T-Rex in the face 100 times
Pilot a VTOL for 1 hour
Kill 1,000 Raptors with the buggy turret
Capture, secure and complete a total of 100 bases
Earn 5,000 Total Assists
Earn 10,000 Total Assists
Kill 5 dinosaurs while in slow motion
Play 10 Survival Matches
Play 25 Survival Matches
Play 50 Survival Matches
Play 100 Survival Matches
Play 10 Rampage Matches
Play 25 Rampage Matches
Play 50 Rampage Matches
Play 100 Rampage Matches
Play 10 Team Elimination Matches
Play 25 Team Elimination Matches
Play 50 Team Elimination Matches
Play 100 Team Elimination Matches
Play 10 Free-For-All Matches
Play 25 Free-For-All Matches
Play 50 Free-For-All Matches
Play 100 Free-For-All Matches
Play 10 King of the Hill Matches
Play 25 King of the Hill Matches
Play 50 King of the Hill Matches
Play 100 King of the Hill Matches
Beat Arid on Hard
Beat Peak on Hard
Beat Slopes on Hard
Beat Raupi on Hard
Win a round on Peak(any difficulty)
Win a round on Arid (any difficulty)
Win a round on Raupi (any difficulty)
Purchase the Wolverine Augmentation 10 times
Purchase the Vampire Augmentation 10 times
Knife-kill 100 Raptors
Stasis Fury kill 100 Rhams
Cloak-kill 100 Dinosaurs
Get 100 Second-Winds
Get revived 100 times
Revive 100 Teammates
Hand out $100,000 in Spiral Credits
Kill 100 Dinosaurs with the Cobra Tank
Purchase every weapon
Taunt 100 times
Power jump 500 times
Feed on 100 dead Raptors with the Vampire Augmentation
Complete Wave 1 on Insane
Complete Wave 2 on Insane
Complete Wave 3 on Insane
Complete Wave 4 on Insane
Complete Wave 5 on Insane
Complete Wave 6 on Insane
Complete Wave 7 on Insane
Complete Wave 8 on Insane
Complete Wave 9 on Insane
Complete Wave 10 on Insane
Kill 100 enemies with the CV-10 Pistol
Kill 100 enemies with the M-40 Magnum
Kill 100 enemies with the CV-10 Silenced Pistol
Kill 100 enemies with the RNC-9 Automatic Pistol
Kill 100 enemies with the C-9 Revolver
kill 100 enemies with the T-99 Dual Pistols
Kill 100 enemies with the MX-4
Kill 100 enemies with the RNC-44 SMG
Kill 100 enemies with the TREK-12 Shotgun
Kill 100 enemies with the TREK-13 Automatic Shotgun
Kill 100 enemies with the FNC-30 Burst Rifle
Kill 100 enemies with the TREK-47 Automatic Rifle
Kill 100 enemies with the TREK-79 LMG
Kill 100 enemies with the X-R8 Tactical Carbine
Kill 100 enemies with the TREK-22 Semi-Automatic Sniper Rifle
Kill 100 enemies with the TREK Longshot Bolt-Action Sniper Rifle
Kill 100 enemies with the TREK Grenade Launcher
Kill 100 enemies with the TREK Rocket Launcher
Kill 100 enemies with the TREK Flamethrower
Kill 100 enemies with the TREK Gatling Gun
Kill 100 enemies with the TREK Energy Carbine
Kill 100 enemies with the TREK Laser Rifle
Kill 100 enemies with the TREK Longbow
Kill 100 enemies with the TREK Ion Blade
Teleport 100 times
Revive 100 downed teammates with the Revital Kit
Kill 100 enemies with the TREK Cryo Knife
Repair a broken generator with the Utility Gun 100 times
Kill 100 enemies with the T-Rex Egg
Kill 500 enemies with the CV-10 Pistol
Kill 500 enemies with the M-40 Magnum
Kill 500 enemies with the CV-10 Silenced Pistol
Kill 500 enemies with the RNC-9 Automatic Pistol
Kill 500 enemies with the C-9 Revolver
Kill 500 enemies with the T-99 Dual Pistols
Kill 500 enemies with the MX-4 Silenced SMG
Kill 500 enemies with the RNC-44 SMG
Kill 500 enemies with the TREK-12 Shotgun
Kill 500 enemies with the TREK-13 Auto Shotgun
Kill 500 enemies with the FNC-30 Burst Rifle
Kill 500 enemies with the TREK-47 Automatic Rifle
Kill 500 enemies with the TREK-79 LMG
Kill 500 enemies with the X-R8 Tactical Carbine
Kill 500 enemies with the TREK-22 Semi-Automatic Sniper Rifle
Kill 500 enemies with the TREK Longshot
Kill 500 enemies with the TREK Grenade Launcher
Kill 500 enemies with the TREK Rocket Launcher
Kill 500 enemies with the TREK Flamethrower
Kill 500 enemies with the TREK Gatling Gun
Kill 500 enemies with the TREK Energy Carbine
Kill 500 enemies with the TREK Laser Rifle
Kill 500 enemies with the TREK Longbow
Kill 500 enemies with the TREK Ion Blade
Teleport 500 times
Revive 500 downed teammates with the Revital Kit
Kill 500 enemies with the TREK Cryo Knife
Kill 500 enemies with the T-Rex Egg
Kill 1000 enemies with the CV-10 Pistol
Kill 1000 enemies with the M-40 Magnum
Kill 1000 enemies with the CV-10 Silenced Pistol
Kill 1000 enemies with the RNC-9 Automatic Pistol
Kill 1000 enemies with the C-9 Revolver
Kill 1000 enemies with the T-99 Dual Pistols
Kill 1000 enemies with the MX-4 Silenced SMG
Kill 1000 enemies with the TREK-12 Shotgun
Kill 1000 enemies with the TREK-13 Automatic Shotgun
Kill 1000 enemies with the FNC-30 Burst Rifle
Kill 1000 enemies with the TREK-47 Automatic Rifle
Kill 1000 enemies with the TREK-79 LMG
Kill 1000 enemies with the X-R8 Tactial Carbine
Kill 1000 enemies with the TREK-22 Semi-Automatic Sniper Rifle
Kill 1000 enemies with the TREK Longshot Bolt-action Sniper Rilfe
Kill 1000 enemies with the TREK Grenade Launcher
Kill 1000 enemies with the TREK Rocket Launcher
Kill 1000 enemies with the TREK FlameThrower
Kill 1000 enemies with the TREK Gatling Gun
Kill 1000 enemies with the TREK Energy Carbine
Kill 1000 enemies with the TREK Laser Rifle
Kill 1000 enemies with the TREK Longbow
Kill 1000 enemies with the TREK Ion Blade
Teleport 1000 times
Revive 1000 downed teammates with the Revital Kit
Kill 1000 enemies with the TREK Cryo Knife
Repair a broken generator 1000 times with a Utility Gun
Kill 1000 enemies with the T-Rex Egg
Beat Strike on Hard
Kill 100 people in Duels
Kill 100 Ion Blade wielding opponents with a gun
Use 100 Sabre Combos
Kill the Deinosuchus 100 times
Pop 100 Raptor heads with the TREK Longbow
Win 5 Duel Matches
Win 10 Duel Matches
Win 25 Duel Matches
Play 10 matches on Nanko
Play 10 matches on Trine
Reach Level 10
Reach Level 15
Reach Level 20
Reach Level 25
Reach Level 30
Reach Level 40
Reach Level 50
Play 5 Instagib Matches
Play 10 Instagib Matches
Play 25 Instagib Matches
Repair 500 broken generators with the Utility Gun
Kill 1000 enemies with the RNC-44 SMG
Spend 1 Game Day in the Arctic
Spend 2 Game Days in the Arctic
Spend 1 Game Week in the Arctic
Spend 1 Game Month in the Arctic
Spend 6 Game Months in the Arctic
Spend 1 Game Year in the Arctic
Play as all 10 Dinosaurs in Rampage
Obtain 100 Compy-Bomb Kills in Rampage
Obtain 100 Rham-Bomb Kills in Rampage
Eat 100 Humans in Rampage
Kill 100 Player-Controlled Dinosaurs in Rampage
Obtain 100 Gatling Sentry Turret Kills
Obtain 100 Flamethrower Sentry Turret Kills
Obtain 100 Rocket Sentry Turret Kills
Obtain 1,000 Melee Kills in any Duel Game Mode
Find a Loot Crate
Find 25 Loot Crates
Find 100 Loot Crates
Find 1,000 Loot Crates
Find All Active Loot Crates in the Arctic
Purchase the Iguana APC
Ride in a 5-Person Iguana APC
Kill a Wild DInosaur in the Arctic
Collect 2 Eggs in one Match of at Least 6 Players
Survive for over 10 Minutes on Slaughter
Get 500 Kills in One Match
Win 10 Team Duel Matches
Play All Toon Based Maps
Beat Conquest Without Dying From the Start
Beat Redikulous Mode