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