Speed Demon Achievement in Halo: The Master Chief Collection

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

First, play on the Easy difficulty setting so that enemies aren't as dangerous. Secondly, don't bother turning on any skull modifiers in the lobby. Lastly, utilizing the various speed running tactics as shown in Halo 3's speed running achievement will help immensely in skipping certain firefights and finishing each mission in a considerably less amount of time as normal. With these tips in mind, you should have no problem completing each mission under Par Time.

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

• Sierra 117 - 15:00 minutes
• Crow’s Nest – 20:00 minutes
• Tvaso Highway – 20:00 minutes
• The Storm – 15:00 minutes
• Floodgate – 15:00 minutes
• The Ark – 20:00 minutes
• The Covenant – 20:00 minutes
• Cortana – 15:00 minutes
• Halo – 20:00 minutes

Overall, just remember to play on the lowest difficulty setting and try rushing past as many firefights when possible. Once you beat the Par Time for all nine missions, this achievement will unlock.