I didn't make it very clear in-game on how to get every single mini-star. If you're having trouble getting them all, here's a guide:

CHAPTER 1:

• Pacifist - Free all the human souls, then fight Omega Jevil until all his HP is at 0.

• Neutral - Free 1 to 5 human souls, then kill Omega Jevil.

• Soulcrusher - Destroy all 6 human souls, then get your soul replaced by the 7th soul.

• Devil - Go fight the secret boss in the basement. You need a minimum of 4 regular stars to access the basement. As long as you complete the challenge in any way, it is good enough to earn a mini-star.

CHAPTER 2:

• Aborted Pacifist - Start the game on the pacifist route, and get a neutral or soulcrusher ending.

• Aggressive Pacifist - Start the game on pacifist route, free all the human souls, then beat Spamton Sigma by fighting.

• Pacifist - Start the game on pacifist route, free all the human souls, then spare Spamton Sigma. You have to attack him at least once, though.

• True Pacifist - Start the game on pacifist route, free all the human souls, then spare Spamton Sigma. You cannot do damage at any point during the fight, otherwise you will get a regular pacifist ending.

• Neutral Pacifist - Start the game on neutral route, then free all the human souls. It doesn't matter if you spare or attack afterward.

• Neutral - Start the game on neutral route, then free 1 to 5 human souls. Then kill Spamton Sigma.

• Neutral Soulcrusher - Start the game on neutral route, then kill Spamton Sigma without freeing any human souls.

• Soulcrusher - Start the game on soulcrusher route, then proceed as normal. It is impossible to free human souls during this route, so there is no redeeming yourself.

• Brutal Soulcrusher - Start the game on soulcrusher route. You need to finish the route when your KARMA is at 13. Typically, Omega Spamton dies at 10 KARMA, but if you only use Snowkid attacks and do the bare minimum amount of damage, you can keep Omega Spamton barely alive until 13 KARMA.