best vs least

best

adv
  • To the most advantage; with the most success, cause, profit, benefit, or propriety. 

verb
  • Had best. 

  • To surpass in skill or achievement. 

  • To beat in a contest. 

noun
  • The person (or persons; or thing or things) that is (are) most excellent. 

  • The supreme effort one can make, or has made. 

  • One's best behavior. 

adj
  • Most; largest. 

  • Most superior; most favorable. 

least

adv
  • Used for forming superlatives of adjectives, especially those that do not form the superlative by adding -est. 

  • In the smallest or lowest degree; in a degree below all others. 

noun
  • Something of the smallest possible extent; an indivisible unit. 

det
  • The most little; the smallest amount or quantity of something. 

prep
  • At least. 

  • What a stupid white privileged POS I am! Least I call myself out. 

  • 2019 December, Justin Blackburn, The Bisexual Christian Suburban Failure Enlightening Bipolar Blues, page 79 

How often have the words best and least occurred in a corpus of books? (source: Google Ngram Viewer )