Here is the full list of all 31 WITCH-BOT MEGLILO achievements.
Complete the Maid outfit
Complete the Mermaid outfit
Beat the game once in HARD mode
Defeat 10,000 enemies
Beat the game once in EASY mode
Complete the Kimono outfit
Beat the game once in NORMAL mode
Defeat 5,000 enemies
Beat LILY
Beat MELIGRO
Beat AMP
Defeat 1,000 enemies
Beat SAKURA
Get a bomb item for the first time
Beat NITORONE
Get a shield item for the first time
Destroy obstacles for the first time
Beat KICHY
Get a satellite for the first time
Use Time Stop Warp for the first time
Beat the game once in INSANE mode
Beat all stages without taking a hit from the enemy
Activate Maximum Bonus for the first time
Get all the satellites
Complete the Reinforcement Parts outfit
Reach a score of 2,000,000 points on EASY mode
Reach a score of 4,500,000 points on NORMAL mode
Reach a score of 7,000,000 points on HARD mode
Reach a score of 9,000,000 points on INSANE mode
Beat LILY ROBOT's secret form
Defeat 30,000 enemies