It varied wildly from unit to unit.
The first three SS divisions (LSSAH, Das Reich, Totenkopf) started off with a poor fighting record because of a lack of experience and overzealousness but by the end of the war had developed a solid reputation.
9th and 10th SS (Hohenstaufen and Frundsberg) were formed later in the war and greatly benefited from the experience gleaned earlier. Maintaining a solid reputation throughout the war.
12th SS (Hitlerjugend) performed unusually well despite being largely made up of Hitler Youth wannabe soldiers. This largely stemmed from the fact 2,000 of its officers and NCOs were transferred from the LSSAH and brought with them the years of experience they had gained fighting in nearly every major campaign.
Einatzgruppen and the Totenkopfverbande were not intended as frontline combat units, mainly being composed of those who had flunked out of Waffen-SS training and wounded who were unfit for service. Their combat record was as could be expected, terrible.
The 36th SS (Dirlewanger) was more of a hazard to itself than it was to the enemy and the Germans were probably better off just executing all of its members themselves.
Waffen Grenadier units (SS units composed of non-German ethnicities) similarly had a wildly varied combat record, with Western volunteers from the Netherlands and Belgium generally performing far better (often on par with the Germans themselves) than their Eastern counterparts who were purely motivated by self-gain and anti-semitism rather than any kind of ideological devotion to National Socialism.