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