Here is the full list of all 20 Gear Gauntlet achievements.
Completed the tutorial
Survive all 10 gauntlets within Loki Tree
Survive all 10 gauntlets within Shard Caves
Survive all 10 gauntlets within Damned Inferno
Survive all 10 gauntlets within Infinite Gear
Collect 5 rare cogs from 5 different gauntlets
Collect 10 rare cogs from 10 different gauntlets
Collect 20 rare cogs from 20 different gauntlets
Collect 30 rare cogs from 30 different gauntlets
Collect 40 rare cogs from 40 different gauntlets
Survive 10 gauntlets with an S grade
Survive 20 gauntlets with an S grade
Survive 30 gauntlets with an S grade
Survive 40 gauntlets with an S grade
Survive gauntlet mode in 99 attempts or under
Destroy 100 barriers of each colour
Collect 5 million life time points
Collect 10 million life time points
Collect 20 million life time points
Contain your rage and attempting a single gauntlet 99 times or more..