Here is the full list of all 100 Mythical Agent achievements.
You have started the game
You saved the soldiers instead of letting them die
Let the Soldiers in the tutorial die
What is he hidding?
Learn of HIVE
You have common sense
How did you manage that?
Advice from a machine.
Save the Mecha Blade in Mission 1
Spend time with Marxwell after Mission 1
Spend time at the lab after mission 1
Spend time with Smith after Mission 1
Let the Yeti live in Mission 2
Kill the Yeti in Mission 2
Stole the keycard from the Yeti
Unlock the secret lab
Spend time with Marxwell after mission 2
Show Marxwell the keycard
Spend time with Smith after mission 2
Who's gonna know?
Beat Mission 3 in record time
Spend a moment to reflect
Spend time with Scythi after Mission 3
Spend time with Kraven after Mission 3
Have Smith die before Mission 4
Actively let the people die in Mission 4
Spend time with Marxwell after mission 4
Remmeber the day it all started
The Day of Burning
Say Goodbye to Scythi after Mission 5
Find the Yeti you spared after Mission 5
Help villages after mission 5
Kill every enemy in Mission 6
Can't save them all
Gather the two capsules in mission 6
Do nothing after Mission 6
Go to the Therapist after Mission 6
Spend time with Smith after Mission 6
Spend time with Kraven after Mission 6
Let the Transport fail in mission 7
Keep the transport alive in Mission 7
Hear what he has to offer
Look around the mansion with marxwell after mission 7
Trying new foods is good for you.
When the tax man comes for the Tengu, don't intervine
Save the Tengu's resturant
Impress the Reaper and accpet his offer
The Reaper is confused why you don't accept it
Invest in a company during Mission 8
Not fast enough!
Take a job with Osiris
Help the bank with repairs
Let the transport die in Mission 9
Transport the souls in Mission 9
Spend time with Karven after Mission 9
Go to Therapy after Mission 9
Discover a dark truth about HIVE