Here is the full list of all 24 Mega Man Legacy Collection achievements worth 1,000 gamerscore.
Unmasked Mr. X and completed Mega Man 6.
Completed all six Mega Man games.
Discovered the truth about Proto Man and completed Mega Man 5.
Escaped the Skull Castle and completed Mega Man 4.
Took out the Alien and completed Mega Man 2.
Earned 1 bronze medal by completing a Challenge.
Earned 1 silver medal by completing a Challenge.
Earned 1 gold medal by completing a Challenge.
Stopped Dr. Wily's plans and completed the original Mega Man.
Turned Gamma to scrap metal and completed Mega Man 3.
Earn 10 bronze medals by completing Challenges.
Earn 25 bronze medals by completing Challenges.
Earn 50 bronze medals by completing Challenges.
Earn 10 silver medals by completing Challenges.
Earn 25 silver medals by completing Challenges.
Earn 50 silver medals by completing Challenges.
Earn 10 gold medals by completing Challenges.
Earn 25 gold medals by completing Challenges.
Earn 50 gold medals by completing Challenges.
Complete the Dr. Wily Forever Challenge.
Complete any Challenge marked with "NO ITEMS."
Complete the "ALL APPEARING BLOCKS" Challenge.
Complete the "ALL ROBOT RUSH" Challenge.
Complete the "ALL ROBOT RUSH (NO ITEMS)" Challenge.