Finish Mass Effect 1, 2 and 3 with the same character

ME3: Make the final assault.

ME3: Defeat a group of Spectre-level opponents on Normal, Hardcore, or Insanity.

ME3: Send a warning across the galaxy.

ME3: Perform any combination of 50 biotic combos or tech bursts.

ME3: Deliver most of the Galaxy at War assets to the final conflict.

ME3: Disable a group of fighter squadrons.

ME3: Overload the shields of 100 enemies.

Establish or rekindle a romantic relationship in all three games in Mass Effect Legendary Edition

ME3: Free Omega from Cerberus Occupation.

ME3: Hijack an Atlas mech.

ME3: Win a political stand-off.