Betcha can't stick it... Achievement in Halo: The Master Chief Collection

Before anything, make sure you load up the corresponding mission on the Easy difficulty. Additionally, go ahead and turn on the Assassins and Bandana skull in the Campaign lobby as this will permanently cloak all enemies in the mission and grant players infinite grenades. Start the mission and as soon as you gain control of the Chief, continue through the doorway and hallway, past the lone Grunt (be sure to kill him), and out into the large courtyard.

Once here, go ahead and switch to Classic Mode because cloaked enemies will be much, much easier to see in the older Halo 2 graphics. Now spot the building straight ahead of you and walk inside. On the bottom floor (or the top floor - it varies) there will always be an Elite roaming around. Although this Elite isn't technically a Stealth Elite, the Assassins skull confuses the game and will consider this enemy to be of the aforementioned rank. With that said, just switch over to your Plasma Grenade, stick the Elite and the achievement will unlock right away!