Halo Infinite

This can be done on any difficulty and done SOLO or in co-op.

Boot up the final mission "Silent Auditorium". You need to clear the starting area and activate the door switch within 3 minutes. Once all the enemies are clear, the music will change. Activate the door and if it was done quick enough, the achievement will pop. If it does not, restart mission and do it again until it pops.

Edit: Thank you Yummy Baklava for pointing out, you should walk through the door to get the achievement to pop. For me it popped before going in the door, I know this because I checked my recorded gameplay and it popped before, but go through the door to be sure! :)

It is most easily done on easy difficulty, your weapon load-out from the open world will be the weapons you start with. The tank gun and/or a rocket launcher would make it a lot easier to do quickly. Hope this was helpful :)

To get the achievement, you must start the "Silent Auditorium" mission.
Once in the mission, you are outside the Auditorium. You must then eliminate all the enemies to open the door and access the Auditorium in less than 3 minutes.

A simple technique is to pick up a heavy weapon (preferably a rocket launcher) from a forward base
and start the mission with the Skull Bandana activated to have unlimited ammo.

Here is a guide to help you:

If you haven't unlocked the Bandana Skull yet, here's a guide that might help:

This achievement can be found in the mission "The Silent Auditorium." I found that an explosive weapon (i.e. a rocket launcher) and a melee weapon such as an energy sword (which can be picked off of the camo elites during the three minute fight) or a gravity hammer was optimal. The bandana skull (infinite ammo) and easy mode is the best combination for this as well.

The second you spawn in at the beginning of the mission, your timer starts. Kill every enemy in a timely manner (I found spamming grenades and comboing with the energy sword and grappling hook worked well), and proceed to open the door and walk through it once all of the enemies are defeated and the achievement should pop. NOTE: THE TIMER STOPS WHEN YOU OPEN AND WALK THROUGH THE DOOR! It does not stop when you defeat all enemies.