On this page of our Halo Infinite guide you'll find a list of activities necessary to complete the game in 100%. By performing the listed activities you'll not only fully fill the progress bar but also obtain achievements related to the campaign.
You can check your progress in the game's main menu. Select Load Game instead of Continue, then highlight your current save slot. The game's completion percentage isn't influenced by difficulty or the multiplayer mode which is considered a separate entity.
To fully complete Halo Infinite's campaign you must:
- Complete all main missions.
- Find all skulls. Note - 5 of 12 skulls are missable, as they can only be obtained during main missions that can't be replayed. If you miss them, you'll have to start a new campaign.
- Find all other secrets - Mjolnir Armor lockers, Spartan, UNSC and Banished Audio Logs, Spartan Cores, propaganda towers, Forerunners' Artifacts. Some collectibles are missable, once again, this applies to the ones found during main missions, in areas inaccessible when exploring the world.
- Reply to all UNSC assistance requests.
- Defeat all 15 important Targets.
- Take over all FOB bases.
- Take over all 7 Banished outposts by completing the missions related to them.