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