Here is the full list of all 50 Ultra Savage achievements.
Reach Level 200
Defeat Unlimited Nightmare Error
Defeat Dr. Congo
Enhanced Item +20
Defeat Unlimited Error
Have Over 10'000'000 HP
Defeat Error
Defeat Oreb and Zeeb
Defeat Githeon The Galactic Conqueror
Reach Level 180
Defeat Xoreb
Have Over 1'000'000 HP
Deal Over 10'000'000 Damage
Reach Level 160
Enhanced Item +10
Reach Level 140
Defeat Nahash
Made A Costume
Do Ten Time Travels
Do Six Time Travels
Deal Over 1'000'000 Damage
Defeat King Bera the Reaper
Reach Level 100
Defeat Lord Pretty Face Coolinagi
Enhanced Item +6
Have Over 100,000 HP
Reach Level 80
Defeat Raki-Raki The Demolisher
Have Over 300% ATK SPD
Maxed Out A Skill
Deal Over 100'000 Damage
Defeat Liki Lee The Amgi-Turner
Deal Over 9'000 Damage
Do Your Second Time Travel
Reach Level 60
Have Over 50% CRIT
Do Your First Time Travel
Have Over 100 CHI
Defeat Heli Boss
Deal Over 1'00 Damage
Reach Fusion Level 10
Defeat Prince of Madness
Reach Level 30
Have Over 150% ATK SPD
Enhanced Item +3
First Enhancement
Reach Level 10
Have over 3'00 HP
Equip a blade and meet Kairon
Do your first fusion