Have feet of clay
Definition 1 of 1
Pro Tip 1/3Hidden Weakness
The phrase suggests a surprising flaw in something or someone that looks perfect. 
The skilled politician, despite her charisma, had feet of clay when it came to financial matters.
Pro Tip 2/3Literary Origin
It originates from the Bible's Book of Daniel, where a statue with feet of iron and clay collapses. 
He was admired like a towering statue but was found to have feet of clay.
Pro Tip 3/3Figurative Use
Used metaphorically, it applies to situations where something apparently strong has a critical flaw. 
The product was revolutionary, yet the company had feet of clay due to poor management.