How many endings are there and what will it take to see them all?
Outcomes(Spoilers)
Collector’s Base Saved in ME2
- Readiness Rating < 1750 – Earth is destroyed regardless of whatever decisions you made.
- Readiness Rating 1750 – Choose to Save the Reapers and the Earth will be saved.
- Readiness Rating 2050 – Choose to become a Reaper and the Earth will be saved.
- Readiness Rating 2350 – Choose to destroy the Reapers and Earth is destroyed.
- Readiness Rating 2650 – Choose to destroy the Repears and the Earth will be somewhat destroyed
- Readiness Rating 2800 – Earth and the Galaxy will be saved once you’re able to create synergy
- Readiness Rating 4000 – Choose to destroy the Reapers and Save Anderson to see Shepard alive.
- Readiness Rating 5000 – Choose to destroy the reapers and fail to Save Anderson to see Shepard alive.
Collector’s Base Destroyed in ME2
- Readiness Rating < 1750 – Earth is destroyed regardless of whatever decisions you made.
- Readiness Rating 1750 – Choose to become a Reaper and the Earth will be destroyed.
- Readiness Rating 1900 – Choose to destroy the Repears and the Earth will be somewhat -destroyed
- Readiness Rating 2350 – Choose to become a Reaper and the Earth will be saved.
- Readiness Rating 2650 – Choose to destroy the Reapers and Earth will be saved.
- Readiness Rating 2800 – Earth and the Galaxy will be saved once you’re able to create synergy
- Readiness Rating 4000 – Choose to destroy the Reapers and Save Anderson to see Shepard alive.
- Readiness Rating 5000 – Choose to destroy the reapers and fail to save Anderson to see Shepard alive.
There are numerous ways to increase readiness and depending on your import save status, single player decisions, multiplayer skill, and multiplayer time, the "most efficient" way to manipulate readiness doesn't really have a universal answer for players.