meaning of can be damning

[Learning_English]

"pretty beautiful" can be damning with faint praise. Its precise nature will be in the tone of voice used.

Could you explain me what the parts in bold mean in this sentence?

In a dictionary, the word damn has a lot of meanings from which I cannot understand this sentence.
_________________
Please let me know if I have made any mistakes in any of my sentences.

[Mister Micawber]

.
The idiom here is 'damning with faint praise'.
.
_________________
Native English teacher at Mister Micawber's