Here is the full list of all 30 Metal Slug 3 achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Clear any mission with no miss
Reach a score of 1 000 000 points with a friend
Kill 500 soldiers
Kill 1,000 soldiers
Play 100 times as Tarma
Unlock all Illustrations
Clear the game without using a continue
Clear the game
Complete all Achievements
Play 100 times as Marco
Play 100 times as Eri
Play 100 times as Fio
Save 1,000 POWs
Reach a score of 500,000 points
Save 100 POWs
Save Hyakutaro Ichimonji
Get all weapons
Throw 300 grenades
Play with all characters
Kill 100 soldiers
Reach a score of 200,000 points
Reach a score of 100,000 points
Obtain items from Madoka Aikawa
Turn into a snowman
Save an orangutan
Throw 50 grenades
Clear Mission 1
Save 10 POWs
Play with a friend
Obtain items from Rumi Aikawa