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