The Lost in Nightmares Add-on for Resident Evil 5 (Xbox 360) has 5 achievements worth 100 gamerscore.
Complete "Lost in Nightmares" on any difficulty setting.
Complete "Lost in Nightmares" with an S rank.
Complete "Lost in Nightmares" on Professional.
Inflict a set amount of damage to Wesker in "Lost in Nightmares."
Destroy all 18 of the Score stars found throughout "Lost in Nightmares."