Required for Platinum → counts toward the bar
conseilHelpful but not mandatory → doesn't count
75 Steam achievements total, no Bronze/Silver/Gold tiers: this guide treats all 75 as a "100%"
Unlocking the 4 class-skill achievements requires having played all 4 base Vault Hunters
Friendship Rules requires a second Steam player: line up a co-op session before going for it
24 achievements are tied to add-ons: 4 paid, plus the free Commander Lilith & the Fight for Sanctuary add-on
Make a manual save right before "Shooting the Moon" (Commander Lilith DLC): one choice there makes an achievement missable
Point of no return
Aside from that one choice, Borderlands 2 is unusually non-missable: no New Game Plus required for the other 74