"Mr. Loughner, you may have put a bullet through her head, but you haven't put a dent in her spirit and her commitment to make the world a better place," former astronaut Mark Kelly said.
U.S. District Judge Larry Burns sentenced Loughner to serve the rest of his life in prison without the possibility of parole. The punishment includes seven consecutive life terms plus 140 years.
"The evidence clearly shows that he knew what he was doing, despite his mental illness," the judge said.
Loughner, 24, spoke just once, confirming to the judge that he would make no statement before sentencing. "That is true," he said.
Beside the dramatic appearance by Giffords and her husband, nine other victims spoke at the sentencing hearing held in a packed federal courtroom in Tuscon.
Kelly, in an interview Thursday evening with CNN's Piers Morgan, said hearing what they had to say "was really a tough thing" for Giffords.
"Gabby said afterwards, for her the biggest emotion was just sadness," Kelly said. "To hear story after story of what the impact of this horrible day had on people was really difficult."
Much of the time, those words were directed toward the 24-year-old Loughner, whose lawyer stroked his arm at times.
"You pointed a weapon at me and shot me," said Susan Hileman, who was wounded by Loughner's Glock pistol. "Over last several months, I wanted to take you by the shoulders and shake you and scream at you."
"It's an awful situation," she said, looking straight at Loughner, "and it's all because of you."
His victims gathered that day "to witness democracy in action," she said. "We brought family and friends. You brought a gun."
Mavanell Stoddard described how her "precious husband," Dorwin Stoddard, was fatally shot as he fell on top of her to shield her from the onslaught of bullets.
"Somehow when you shot him, I got out from under him," Stoddard said. "I was screaming 'Oh God, oh God, help me.' I said to him 'breathe deeply,' and he did. Therefore, I believe that he heard me said 'I love you.' "
He died in her arms her minutes later, she said. "Then I passed out because you had shot me three times," she said. "You took away my life, my love, my reason for living."
"I am so lonesome," Stoddard said as she stared directly at Loughner. "I hate living without him. No one to hold me, no one to love me, no one to talk to, no one to care. I forgive you. As a Christian, I am required to."
Mary Reed, who was among the wounded, blamed Loughner for introducing "my children to something sinister and evil."
"My children will forever remember the moments of people when they died, the smell of blood everywhere," Reed said.