Here is the full list of all 28 Endling - there are Extinction is Forever achievements.
Finish the game with all cubs alive.
Finish the game with at least three cubs alive.
Finish the game with at least two cubs alive.
Finish the game with at least one cub alive.
Release the Badger from the trap.
Reunite the Badger's cub with their mother.
Rescue the missing cub.
Reach the first lair.
Reach the second lair.
Reach the third lair.
Finish the game.
Find all traces of the missing cub in the river area.
Find all traces of the missing cub in the forest.
Find all traces of the missing cub near the dumping ground.
Learn all cub skills.
Let the Scavenger pet you.
Let your cubs eat every kind of food in the game.
Pet your cubs at least once for five days straight.
Bark three times in a row when it's raining.
Do not kill any animal (fish, mouse, rabbit, pigeon, chicken) for five days.
Enter your lair with a full stomach.
Bark at the Roamer.
Don't feed your cubs trash for six days in a row.
Let Molly pet you.
Hunt a chicken for the first time.
Pet a scared cub.
Have your cubs eat the Easter Egg.
Unlock every other achievement in the game.