Here is the full list of all 35 The Lord of the Rings: The Battle for Middle-earth II achievements worth 705 gamerscore.
Lose to someone ranked 20 places below you
Win a game against someone 20 places higher than you
Win 10 Capture and Hold games Unlocks Hero: Avatan
Complete Evil Withered Heath with all bonus objectives (Level 6)
Complete Evil Campaign without a Hero dying Hero: Urulooke
Complete Evil Erebor with all bonus objectives (Level 7)
Complete Evil Rivendell with all bonus objectives (Level 8) Unlocks Hero: Olog
Complete Evil Campaign Unlocks Hero: Tumna
Win 10 Hero Vs Hero games Unlocks Hero: Felek
Win 10 Versus games Unlocks Hero: Ohta
Lose 10 Multiplayer matches in a row
Complete Evil Mirkwood with all bonus objectives (Level 5)
Complete Evil Shire with all bonus objectives (Level 3)
Complete Evil Fornost with all bonus objectives (Level 4) Unlocks Hero: Thrugg
Complete Evil Grey Havens with all bonus objectives (Level 2)
Win 1 Single Player Skirmish game
Win 1 Hero Vs Hero game
Win 1 Capture and Hold game
Win 10 Resource Race games Unlocks Hero: Celebrim
Win 1 Resource Race game
Win 10 King of the Hill games Unlocks Hero: Fhaleen
Win 1 King of the Hill game
Complete Good Rivendell with all bonus objectives (Level 1) Unlocks Hero: Hadhod
Complete Good Grey Havens with all bonus objectives (Level 5)
Purchase first player power
Complete Evil Lorien with all bonus objectives (Level 1) Unlocks Hero: Krashnak
Complete Good Dol Guldur with all bonus objectives (Level 8) Unlocks Hero: Idrial
Complete Good Campaign without a Hero dying Hero: Mektar
Complete Good Campaign Unlocks Hero: Berethor
Complete Good Erebor with all bonus objectives (Level 7)
Complete Good Celduin with all bonus objectives (Level 6)
Win 1 Versus game
Complete Good Blue Mountains with all bonus objectives (Level 4) Unlocks Hero: Maur
Complete Good Ettenmoors with all bonus objectives (Level 3)
Complete Good High Pass with all bonus objectives (Level 2)