Here is the full list of all 12 Machine Gun Train Run achievements.
Complete any level in Campaign Mode with a 1-star ranking.
Complete Campaign Mode and reach the ending.
Get a 5-star rating on every level in Campaign Mode.
Complete the Campaign Mode in co-op.
Reach the end in Speedrun Mode.
Complete Speedrun Mode in 15 minutes or less.
Complete Speedrun Mode in co-op.
Reach 100,000 points in Endurance Mode on Easy.
Reach 100,000 points in Endurance Mode on Normal.
Reach 100,000 points in Endurance Mode on Hard.
Reach 500,000 points in Endurance Mode on any difficulty.
Reach 1 million points in Endurance Mode on any difficulty.