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