Here is the full list of all 25 Solar 2 achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Steal 10 planets on the "Planet Stealer" challenge mission.
Get 4 points in the star challenge mission "Snowball Fight".
Complete every challenge mission with a hard level score.
Complete every challenge mission with any score.
Start the 3rd part of the "Duel" mission as a single star with no planets and beat it in under 3 minutes.
Why?
Kill all the attacking ships in the first part of the "Heist" mission before completing it.
Complete the 2nd part of the "Fine Art" mission without dying and without evolved life on your planet.
Complete the second part of the "Concert" mission with no evolved life on your planet.
Complete the first part of the "Concert" mission in under 1 minute.
Complete each of the "Assassin" mission parts without dying.
Beat the final boss as a dark matter star without using Physics or God options.
As a star have an orbiting life planet with 100 kills.
Get the maximum possible life in your system.
Make a 40 star system.
Grow to a black hole from a multi star system.
Go from Big Bang to Big Crunch in under 20 minutes. No menu respawning.
Go from a small black hole (<150k mass) to Big Crunch without the interface visible.
What is the entity?
Beat all the missions without using Physics or God options.
Get 10 planets in your system orbiting clockwise.
Get Lost.
Make a 6 star system.
Grow so large you absorb the whole universe.
Have 15 asteroid moons around your planet.