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