Learn English – Terminology – What is the exact word to describe ‘being skeptical of something/someone’

It sounds like the literary device term you're looking for is creating a foil where a foil is another character in a story who contrasts with the main character, usually to highlight one of their attributes.

Juxtaposition is a literary device wherein the author places a person (etc) parallel to another in order to highlight the contrast between the two and compare them.

Non-literary comparisons would be setting up a false equivalency, rigging the deck, or stacking the deck: to manipulate events, information, etc., in order to achieve an advantage or desired result.

"Tip-of-the-tongue" is used to refer to situations in which a person knows a word but cannot produce it at the time. We say--when trying to answer a question--"It's right on the tip of my tongue."