Here is the full list of all 10 XenoRaptor achievements worth 1,000 gamerscore.
Kill 2,000 enemies with the chaingun.
Kill the first boss.
Complete Dreadnought battle.
Complete Terror Fortress Omega battle.
Unlock 20 items.
Score 100,000 points.
Score 1,000,000 points.
Kill 1,000 enemies with lasers.
Kill 500 enemies with the blaster.
Kill 1,000 enemies with missile.