1. In the best possible scenario. At best, Doug will be only an hour late. They're only selling junk at the yard sale, so I think they'll make $10 at best.
2. Ideally suited for success. In this usage, a pronoun is used between "at" and "best." I'm not at my best when I'm tired.
1. In the worst possible scenario. In this usage, "the" can be used between "at" and "worst." At the worst, Doug will be an hour late. They're selling some nice stuff at the yard sale, so I think they'll make a few hundred bucks at worst.
2. In one's least positive, effective, or successful state. In this usage, a pronoun is used between "at" and "worst." I'm at my worst when I'm tired. The team is at their worst when they're not working together.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
at bestand at most
in the most favorable view; in the most positive judgment; as the best one can say. At best we found their visit pleasantly short. The dinner was not at all pleasant. At best the food was not burned. At most there were three people in line ahead of me.
at one's best
1. and at its best to the utmost; to the highest degree possible. This restaurant serves gourmet food at its best. The singer was at her best when she performed ballads.
2. in the best of health; displaying the most civilized behavior. (Often in the negative.) He's at his best after a good nap. I'm not at my best when I'm angry.
at (the) worst
in the most negative or pessimistic view. At worst, Tom can be seen as greedy. Ann will receive a ticket for careless driving, at the worst.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
Under the most favorable circumstances, as in At best we'll be just one week behind schedule, or Cleaning out the attic is a tedious job at best. This idiom, formerly also put as at the best, today is most often used in situations that are actually far from ideal, as in the examples above. [First half of 1300s] For an antonym, see at worst.
Also, at the worst.
1. In the least favorable circumstance; under the most difficult conditions. For example, Convicted of taking a bribe, the official believed that at worst he would be sentenced to a few months in prison . [1500s]
2. In the least favorable view or supposition, as in No harm done; at the worst I'll copy the tax return again. Chaucer used this sense in Troilus and Cressida: "For at the worst, it may yet short our way." [Late 1300s] For the antonym, see at best.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
at ˈbest/ˈworsttaking the most/least hopeful or positive view: Smoking is at best unpleasant and expensive, and at worst lethal.
Farlex Partner Idioms Dictionary © Farlex 2017
1. Interpreted most favorably; at the most: no more than 40 people at best in attendance.
2. Under the most favorable conditions: has a top speed of 20 miles per hour at best.
at (the) worst
Under the most negative circumstances, estimation, or interpretation: At worst, the storm will make us postpone the trip.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.