Formal:
* The scientist's thoroughness in her research ensured accurate and reliable results.
* The lawyer's thoroughness in reviewing the case allowed him to anticipate every potential argument.
Informal:
* I was impressed by the throughness of her cleaning; the house was spotless.
* He approached the task with a surprising amount of throughness, leaving no stone unturned.
Figurative:
* The throughness of her gaze seemed to penetrate my very soul.
Remember, "throughness" is a relatively uncommon word, so it's best used in formal settings or when you want to emphasize the depth and completeness of an action.