Compliments corrupt a person better than insults.
If you want to destroy someone, give them an inflated opinion of themselves and watch as they fail to live up to their own expectations. If you want to create something beautiful, you must begin with a foundation of realism because once you strip everything else away that is all that is left.
Possible theories for the harmful effect of compliments: Spotlight Effect is increased, Self-efficacy is decreased, Ego grows and shift from growth strategy to maintaining social status e.g. as smart, instead of improvement strategy.