Here is the full list of all 20 Highwater achievements.
Collect all newspapers
Collect all books
Collect all boosters
Successfully avoid the battle at the Cinematheque
Beat the Vikings with all generators undamaged
Chain four attacks with Josephine in any battle
Interrupt five actions with Nikos’ camera
Complete the optional combat in Chapter 3
Don’t let a single Alphavillian citizen die in Alphaville
Pet the dog in the Botanical Garden two times in a row
Finish the Botanical Garden without petting the dog
Take Mark, the self-immolating Alphavillian, with you
Tornado kick 3 enemies in one action with Laura
Hack each kind of robot (Drone, Dog and Yellow Robot) with Lin
Take the basketball to Hightower
Kill the doctor using Pigman
Enter Alphaville
Accept the terms of service
Complete the game
Complete all achievements