Here is the full list of all 51 Mugen Souls achievements.
Saw the true ending.
Won a battle in the Mugen Field with all commands sealed.
Saw the normal ending.
Reached the 50th floor of the Mugen Field.
Dealt 1,000,000 points of damage.
The seven worlds are all yours now!
Obtained more than 50 types of shampurus.
Dealt 100,000 points of damage.
Made the hero and demon lord of Metal World into your peons!
Made the hero and demon lord of Tree World into your peons!
Made the hero and demon lord of Water World into your peons!
Dealt 10,000 points of damage.
Made the hero and demon lord of Fire World into your peons!
Obtained more than 20 types of shampurus.
Be a victim of your own Peon Ball.
Destroyed an object in the air.
Entered the Mugen Field for the first time.
Activated Fever Mode.
Performed a combo with at least 100 hits.
Made the hero and demon lord of Moon World into your peons!
Checked out the stat-boosting hot spring for the first time.
Activated a Triple Counter Stop.
Made the hero and demon lord of Sun World into your peons!
Turn a continent into your peon.
Successfully get a preemptive attack.
Performed a Blast Off attack.
Won a G-Castle battle.
Successfully make an enemy your peon.
You started the game. Great work!
Unlocked all trophies. Are you an undisputed god now, too!?
Reached the 100th floor of the Mugen Field.
Learned all G-Castle skills.
Dealt 10,000,000 points of damage.
Dealt 100,000,000 points of damage.
Performed a combo with at least 999 hits.
Activated a Triple Counter Stop at full power.
Reached Level 999.
Reached Level 9999.
Used Peon Fusion over 10 times.
Performed a Blast Off attack at maximum power.
Unlocked a hidden Job.
Unlocked all Jobs.
Held more than 100,000,000 G.
Obtained more than 999,999,999 Mugen Points.
Increased Chou-Chou's Charm Level beyond the 50 percent mark.
Defeated all the doppelgangers.
Defeated the Sun Goddess.
Obtained all types of shampurus.
Dealt 10,000,000,000 points of damage.
Increased Chou-Chou's Charm Level to 100 percent.
Made a Peon Ball over 10,000,000,000 Km in size.