Required for Platinum → counts toward the bar
conseilHelpful but not mandatory → doesn't count
Gears of War: E-Day doesn't exist on PlayStation: this guide treats the 54 Xbox achievements (1,000 Gamerscore) as a "100%", with no Platinum language
One shared achievement list on Xbox Series X|S and PC: Xbox Play Anywhere progress syncs between both versions
0 missable achievements: chapter select lets you go back for any Hard Case, Supply Cache item, or Secondary Objective you missed
3 achievements require Insane difficulty: plan a dedicated run for it after a first playthrough on a lower difficulty
The real bottleneck for 100% isn't the Campaign: it's the Horde Siege and Versus grind (50,000 Horde kills, 25,000 Versus kills, player level 100, 4 maxed classes)
"You're My Brother" requires finishing the whole Campaign in co-op: it can't be caught up on solo