Short answer: In the U.S., 12 standard deviations.

In the U.S., deaths were 16%-17% higher than expected. The death rate was 17.8% higher than in 2019. Excess deaths were higher in 1918, but every other year since 1900 is lower.

Using 1946-2019 as our sample, the average yearly change in death rate is -0.2% with a standard deviation of about 1.47 (percentage points). The biggest increase in this year range was 3.1% (2.2σ).

If we go back before the antibiotic era, the biggest one-year increases are in 1918 (29.3%) and 1929 (7.2%). Note that statistics before 1933 don't include all states.

For some other ways of looking at the data, here's an economists blog post: https://economistwritingeveryday.com/2021/01/06/excess-morta...

(He was writing in January, so had less complete stats.)