Here is the full list of all 20 NEON Ultra achievements.
Die for the first time
Kill 100 enemies in one game
Achieve a 10x Combo
NEW_ACHIEVEMENT_DESC_1_2
Achieve a 300x Combo
Achieve a 600x Combo
Survive for 120 seconds without shooting once
Kill 100 enemies without taking damage
Amass a score of 500,000 in one game
Amass a score of 777,777 in one game
Amass a score of 1,000,000 in one game
Amass a score of 5,000,000 in one game
Amass a score of 10,000,000 in one game
Played 50 full games of NEON Ultra
Played 100 full games of NEON Ultra
Keep a shield active for 60 seconds
Kill 500 enemies in one game
Kill 800 enemies in one game
Reach maximum weapon power
Kill 15 enemies without moving