Here is the full list of all 30 Causal Nexus achievements.
Start the game
Finish the tutorial
Kill a boss
Kill 10 000 opponents
Kill 1000 elit opponents
Kill 10 bosses
Finish the cyan challenge
Finish the yellow challenge
Finish the magenta challenge
Finish the last healing challenge
Finish the last maze challenge
Finish the last jumping rope challenge
Finish the last life symbiosis challenge
Finish the last timed waves challenge
Unlock 3 characters
Make a 2 skill chain
Make a 3 skill chain
Make a 4 skill chain
Get 5 bonus objectives
Get 10 bonus objectives
Get 20 bonus objectives
Kill 1 000 000 opponents
Kill 1000 bosses
Beat level 24
Beat level 36
Beat level 48
Beat level 60
Beat level 72
Beat level 120
Fully fill the grid