Never one to mince his words, Antonio was the perfect dissembler; even an outright fabrication was delivered with aplomb.
Bold part is OK. However, I am really struggling to understand other parts.
"Never one to mince his words": What is the subject of the sentence? What is the tense used? What does "to" stand for in the sentence?
"even an outright fabrication was delivered with aplomb": Why the sentence is passive past? Does passive past makes the sentence sarcastic?