If you describe something such as someone's behaviour or appearance as impeccable, you are emphasizing that it is perfect and has no faults. [...]

What is the meaning of an impeccable?

1 : free from fault or blame : flawless spoke impeccable French. 2 : not capable of sinning or liable to sin.

What makes someone impeccable?

The adjective impeccable describes something or someone without any flaws. ... The adjective impeccable refers to something or someone without marking or error — but it can describe something spotless or clean. The word comes from the Latin impeccabilis, "to be sinless," which is also an outdated sense in English.