Better With Age Achievement in Halo: The Master Chief Collection

Before anything, make sure to turn on "Scoring HUD" in the Campaign Lobby before starting a mission. In order to achieve the Par Score on all ten missions with Halo 3's Campaign, you will want to take three things into account.

First, manually activate the Cowbell, Famine, Fog, Grunt Birthday Party, Thunderstorm, and Tough Luck skulls in the lobby and set the difficulty to Heroic. If the mission is exclusively a Flood-oriented mission, such as Floodgate and Cortana, go ahead and activate the Catch skull. Since Flood do not throw grenades, this essentially becomes a free multiplier.

Unfortunately, Par Scores cannot be obtained in Co-Op play, so just stick with a solo playthrough of each mission here. Secondly, you will want to try completing the mission as quickly as possible (finishing under Par Time will give a x3 multiplier to your final score) while still killing everything on the battlefield via headshots and multikills; do not skip firefights or leave anyone alive. Lastly, if you do happen to run over Par Time, try picking up the pace as the time multiplier will begin to reduce significantly!

You can use the checklist below for a reference on each mission’s Par Score:

• Sierra 117 - 13,000
• Crow’s Nest – 19,000
• Tvaso Highway – 21,000
• The Storm – 15,000
• Floodgate – 25,000
• The Ark – 25,000
• The Covenant – 25,000
• Cortana – 17,000
• Halo – 24,000

Once you beat the Par Score for all nine missions, this achievement will unlock.