Oh, no, he did much worse:

He switched her brain with that of a chicken (with Magic!), then burned the chicken alive—in her body—so that the chicken’s thrashing around in horrible agony left marks around the room (while he forced Narcissa to watch, with Magic!). Then he kept Narcissa alive (with Magic!) in the chicken’s body, to keep company to Fawkes; he kept her hidden (with Magic!) right near his perch, so that every time Fawkes re-spawned she was reminded of what her captor was capable of. Then he burned her in front of Harry (with Magic!) just because he thought it was funny :-)

By the way, Lucius is not actually mad because he killed her—Dumbledore told the first part the above to him, but he kept silent about the details because it was embarrassing to have his wife turned to a chicken. That’s why Dumbledore had trouble during the trial; he felt a bit embarrassed about having killed Narcissa after all.

Also, Draco actually picked “fire” as his army’s symbol because he’s secretly fantasizing about being burned alive.