And Dachau isn‘t the worst by a long shot.
The camps in Germany that see the most visitors, especially Dachau, conveniently close to Munich, Oktoberfest and all that, were hellish places, and many Jews were among the victims held and murdered there.
But they were originally built by the Nazis to hold political prisoners, and continued to primarily have that function. In the 30s some prisoners actually served time in Dachau and were released. Horrific as these camps were, they weren‘t really part of the plan for the Holocaust.
For that you have to go to what was then German-occupied Poland. Auschwitz had a dual purpose as a slave labor depository for industries that were encouraged to build in the vicinity, and as an extermination site for those who could not work, and later for Jews deported from Western Europe in general. And for the most intense phase of the Holocaust, the so-called Operation Reinhardt 1942/43 which killed the remaining 1.8 million Polish Jews, killing sites were built that weren‘t really concentration camps because the victims didn‘t live long enough to need a camp: Treblinka, Belzec, Sobibor.
There, the Nazis actually tried to cover their tracks. Not much to see there nowadays except monuments.