Quality changing promos (they all require Size Matters).
Upward (unit level required)
Unearthly Ability (Epic -> Divine) - LV. 20
Legendary Prowess (Elite -> Epic) - LV. 15
Unbelievable Expertise (Exceptional -> Elite) - LV. 11
Astonishing Acumen (Superior -> Exceptional) - LV. 8
Absolute Proficiency (Standard -> Superior) - LV. 6
Natural Talent (Mediocre -> Standard) - LV. 4
Better Skill (Poor -> Mediocre) - LV. 3
Emerging Competence (Inferior -> Poor) - LV. 2
Learned Aggression (Pathetic -> Inferior) - LV. 1
Barely Capable (Incapable -> Pathetic)
Downward (no level requirement, stuck as WIP):
Fallen Grace (Epic <- Divine)
Tarnished Supremacy (Elite <- Epic)
Eroded Superiority (Exceptional <- Elite)
Once Great (Superior <- Exceptional)
Simply Average (Standard <- Superior)
Slightly Entropic (Mediocre <- Standard)
Jaded Decadence (Poor <- Mediocre)
Paralytic Personality (Inferior <- Poor)
Absolute Enfeeblement (Pathetic <- Inferior)
Completely Incapacitated (Incapable <- Pathetic)
It was Might promotion, that is tied to lifestyle techs and to quality levels.
Thanos was Superior quality before getting infinity stones, and each one was equivalent to Quality Up promotion 
Or Ironman upgrading his suit.