Wallenberg didn't actually have the authority to do much, since the Swedes were staying neutral at the time, but he wasn't going to let a little thing like inability to do anything stop him from doing something. During his tenure at the Swedish embassy, he started mocking up fake passport documents called "schultzpasses" that granted Jews a free ticket to Sweden. While this is kind of like infiltrating the Pentagon by writing the word "pass" on a napkin, the official-looking schultzpass papers went largely unquestioned.
And Wallenburg's heroic bullshit didn't stop there. He soon began renting apartment buildings all over Budapest, brazenly declaring them Swedish diplomatic territory and packing them full of Jews, again without any authority whatsoever. Apparently afraid of pissing off mighty Sweden, the Nazis couldn't set foot inside and were reduced to standing on the sidewalk and just shaking their fists at the buildings.
"Ten marks if you can hawk a loogie into the Oberleutnant's hat."
Thanks largely to Wallenburg's diplomatic con job, thousands of Jews held off a trip to the gas chambers before the Soviet army marched in to push out the Nazis. By that time, Adolf Eichmann tried to step up the extermination by just burning down some Jewish ghettos. Not on Raoul Wallenburg's watch. He directly confronted Eichmann and told him to his face that he would personally see him hanged. Eichmann, seeing the viking blood welling up behind Wallenburg's eyes, called off the massacre and fled Budapest, saving 70,000 lives. Who ever said diplomacy doesn't accomplish anything?
As a reward for his heroism, the Russians arrested Wallenburg and made him disappear forever.
Don't you just love happy endings?