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