Karl Brandt.

SS Gruppenfuehrer (group leader) in the the Allgemeine SS and SS Brigadefuehrer (equivalent to Generalmajor) in the Waffen-SS. He headed the administration of the Nazi euthanasia program and was Adolf Hitler’s personal physician. He was involved in criminal human experimentation. Brandt performed a great number of abortions on women deemed genetically disordered, mentally or physically handicapped, or racially deficient. 

He was a member of Hitler’s tight inner circle at Berchtesgaden, which included Eva Braun, Albert Speer and Heinrich Hofffmann. Brandt was said to be very close to the Fuehrer but shortly before the war ended Brandt had sent his wife, Anni, and their son towards the American line in hopes of evading capture by the Russians. Brandt was arrested by the Gestapo but evaded execution thanks to the intervention of Albert Speer and Heinrich Himmler

However, due to his involvement in euthanasia and human experiment, after World War II  he was convicted of crimes against humanity by the Allies and was hanged on June 2nd 1948.

I feel like Karl Brandt is often one of the forgotten evils of the Third Reich, he’s certainly less talked about among the general people anyway. I’m just doing a little reading while I’m sick, this is all just the very basics you can find with a simple wiki search but enjoy!