Wrong Lemmy headline, the graphic is about "death penalty for non military crimes", which implies that there were death penalty executions after those years on the map.
As an example, in Belgium the last execution was in 1950, by firing squad. The Belgian state had extended the state of war to be able to put war criminals & collaborators in front of military tribunals. That last 1918 execution by guillotine was also ordered by a military tribunal, it was a Belgian soldier who had murdered one of his two fiancées plus her unborn child: https://nl.wikipedia.org/wiki/Emile_Ferfaille Had he not been a soldier, he would most likely not have been executed. The last execution in Belgium that was ordered by a civil court happened in 1863.
Civil + military capital punishment was only officially abolished in 1996 in Belgium, so about 133 years between the decision to stop doing it , and actually putting that into law. And a few months after the law was officially changed, the serial murderer + pedophile Dutroux was arrested, after which there was a lot of public support for the death penalty again. A bit of fortunate timing in unfortunate times.