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