Don't Touch That!

From Halopedia, the Halo wiki

Don't Touch That!

Don't Touch That! is an achievement for Halo: Reach multiplayer matchmaking added to the Defiant Map Pack with the release of Halo: Combat Evolved Anniversary. The achievement was earned by preventing the attacking team from touching the flag in a matchmaking 1 Flag CTF game. This applied not just to one round, but to the entire game. Thus as most 1 Flag CTF games were two rounds, players needed to prevent the opposing team from touching their flag in either of them. It could only be unlocked on a Defiant map.

Following the shutdown of Xbox 360 Halo online services on January 13, 2022, this achievement is no longer attainable.[1][2]

The achievement is worth 25 Gamerscore.