Shiny... Achievement in Halo: The Master Chief Collection

When this mission begins, hop inside a Scorpion Tank and proceed through the mission as normal until you reach a circular courtyard and the “Kizingo Boulevard” gate/checkpoint. At this time, one of your marines will open the gate and on the other side there will be dozens of Covenant units and several Wraiths, Ghosts, and Banshees. Destroy all the ground units – including the Wraiths and Ghosts – but keep both Banshees in tact; do not shoot at them! When only the Banshees remain, drive your Scorpion onto the streets and follow the roundabout, proceeding up the hill towards a back alley/street. 

Hop out of the Scorpion and try to get the Banshees’ attention so that they fly into this alley. If lured properly, they will fly towards the ground and eventually get stuck, unable to turn around or pilot away. At this point, position yourself underneath the pilot seat and you should see the Brute’s feet. Using whichever weapon in currently in your hands, begin to shoot at the Brute’s feet (not the Banshee) while simultaneously holding the “board/action” button. Once you kill the pilot while holding the "board/action" button, your character will automatically climb into the Banshee before it explodes, thus unlocking the achievement.