Here is the full list of all 27 Gear Up achievements.
Drown in the water at least once.
Destroy 20 enemies with the Grayhound (saws).
Destroy 10 enemies with the default starter cannon.
Destroy at least seven different opponents in a team game mode.
Repair (1250) armor in one round of a team game mode.
Repair 30000 armor in lifetime.
Destroy 1500 enemies
Win 20 team deathmatch rounds.
Win 20 deathmatch rounds.
Assist in capturing at least 20 conquest towers in a single round.
Win 20 conquest rounds.
Win 3 conquest rounds.
Win a Conquest round overwhelmingly, with a ratio of 4:1 or higher.
Win a TDM round overwhelmingly, with a ratio of 4:1 or higher.
Recieve 500 damage without being destroyed in a round.
Killed a deserting enemy
Back playing after more than one week of Gear Up absence.
Destroy 25 enemies
Destroy 50 enemies
Destroy 75 enemies
Destroy 100 enemies
10 kills in a row
6 kills in a row
4 kills in a row
3 kills in a row
2 kills in a row
Capture a conquest tower together with 3 or more teammates.