1. Under the worst conditions; as the worst possibility.
When Don was caught cheating in the examination he thought that at worst he would get a scolding.
Compare: AT MOST.
Contrast: AT BEST.
2. In the least favorable view, to say the worst about a thing.
The treasurer had certainly not stolen any of the club's money; at worst, he had forgotten to write down some of the things he had spent money for.