Here is the full list of all 20 Paladin achievements worth 1,000 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox One.
Collect a total of $35,000 cash
Kill boss at end of level 40
Score a total of 500,000 points
Kill all aliens on level 35
Collect a total of $25,000 cash
Kill boss at end of level 30
Kill all aliens on level 25
Kill boss at end of level 20
Kill all aliens on level 15
Score a total of 100,000 points
Collect a total of $5,000 cash
Kill boss at end of level 10
Score a total of 50,000 points
Kill all aliens on level 5
Score a total of 25,000 points
Fill the rage counter to 100%
Collect a total of $1,500 cash
Fill the rage counter to 75%
Fill the rage counter to 50%
Fill the rage counter to 25%