What are all of the Challenge tiers?

[Kuro]

According to my good friend Box Thinker his challenge badge currently has these tiers which have been so nicely sorted by rarity

Unlikely:
Heartless
Omnipotent
Noodler
Cyantific
Sorrowful
Otterly
Lightweight
Flamboyant
Flownoomder
Aggro-magnet
Kief Daddy's
Pretty Pink
Terranable

Rare
Armadillius
Doctorate
Vakarian
Irradiated
Rotting
Decimating
Yagginese
Shank's Surplus
Exalted

Legendary:
Apocalyptic
Axistence
Kaiju