A person or thing that chastens; something that subdues, humbles, or punishes.
From 'chasten' plus the agent noun suffix '-er,' creating a word for whoever or whatever performs the action of chastening (typically from the 16th century onward).
Life itself is often described as a 'chastener'—difficult experiences and failures humble us and teach us lessons that no amount of praise ever could, which is why ancient philosophers valued hardship.
Complete word intelligence in one call. Free tier — 50 lookups/day.