Regnant
Reigning, ruling
Nuance
Variation, shading
Pernicious
Destructive, harmful
Recalcitrant
Defiant, unmanageable
Perplexed
Baffled, puzzled
Reservoir
Pool, lake
Ruminate
Consider
Somnolent
Drowsy, sleepy
Impetus
Momentum, impulsion
Abrasive
Polish, rubbing
Unctuous
Servile, fawning
Temerity
Boldness, nerve
Odious
Offensive, disgusting
Mitigation
Ease, reduction
Insurgency
Uprising, revolt