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