You’re likely thinking of the notorious Dirlewanger Brigade, led by infamously sadistic necrophile, alcoholic and rapist Doktor Oskar Dirlewanger, which unit was filled with convicted criminals and other undesirables recruited from prisons and concentration camps.
Dirlewanger himself had been in trouble for various odious crimes, including raping a 14 year old girl, prior to the war, but his disgrace was short-lived, and he was rehabilitated (and his doctorate, in political science, reinstated) for pragmatic reasons, it seems; his willingness to do things that most normal people would consider unthinkable a useful asset in the amoral environment of the SS.
His disgusting sexual proclivities and intense cruelty and sadism meant that the unit he led was given more or less free rein, to murder, torture, rape and burn. They started life guarding a concentration camp, and the cruelties inflicted on the prisoners by Dirlewanger and his criminal cronies were so evil as to almost defy belief.
Thereafter, they were moved on to Belarus where they took action against “gangs”, basically a euphemism for terrorising the population, with rape, torture and extortion aplenty. Dirlewanger and his brigade, a division at this point, was eventually shot to pieces by the Red Army during Operation Bagration, and then reformed to suppress the Warsaw Uprising, with more of the cruelty and sadism that had come to characterise the unit, and for which Dirlewanger was promoted and received the Knight’s Cross.
Oskar Dirlewanger himself survived the war, but not for long. He died in a prison camp in 1945; most likely he was beaten to death by the guards.
You may also be thinking of the Kaminski Brigade, led by Bronislav Kominski, pictured below, which was a unit of the Waffen SS formed from Soviet nationals who for whatever reason chose to collaborate with the Nazis.
Similar to the antics of the Dirlewanger Brigade, the Kaminski Brigade was noteworthy for their evil practises behind the lines, and during Operation Bagration and the Warsaw Uprising. Rape and torture, as well as large scale murder of the civilian population, characterised these men, much to the disgust of the Army and even the SS, which recognised the unruly and ungovernable nature of the unit, dissolving it in 1944.
