Explanation:

- The word "redoubtable" often refers to someone or something that is formidable, worthy of respect, or commanding respect due to power, capability, or excellence.

- Flimsy: Suggests something that is weak or without substance. It's nearly the opposite of redoubtable.

- Perplexing: Means confusing or puzzling. While intriguing, it doesn’t convey the respect or might associated with redoubtable.

- Formidable: This indicates someone or something that causes fear, respect, or awe due to impressive power or ability, closely aligning with redoubtable.

- Voluble: Refers to someone who is talkative or loquacious. It doesn't connect with the sense of awe or strength.