The American skier joined Ingemar Stenmark as the only men in the 47-year World Cup history to get six GS victories in a season. Stenmark's 10-race sweep in 1978-79 is the record.
"It's very surreal for any ski racer," Ligety said of being likened to the Swedish great. "He is at another level that's not really achievable."
Ligety's 17 career World Cup wins in his specialist event are a long way from Stenmark's 46, though the latest came with similar authority.
He raced smoothly down the steep slope in a two-run time of 2 minutes, 14.76 seconds, beating overall World Cup winner Marcel Hirscher by 0.37 seconds.
Hirscher was runner-up to Ligety for the fourth time, and French prospect Alexis Pinturault trailed by 1.16 in third.
The 28-year-old Ligety had three previous GS discipline titles, but this was his best season yet and included three world championship gold medals.
His six World Cup wins came from eight races, and he placed third in the other two, won by Hirscher and Pinturault.
"This year in general has been a great year. It's going to be a difficult one for me or anyone to achieve," said Ligety, who never let up after dominating the traditional season-opener in Austria. "It's been so great, just from Soelden at the start winning by 2.7 (seconds)."
He also broke 1,000 World Cup points overall and will finish third in the standings. Both are career bests.
Ligety completed an American victory double in glorious sunshine at the World Cup finals in Lenzerheide. One hour earlier, Mikaela Shiffrin delivered a come-from-behind victory to edge Tina Maze for the women's slalom title.
That ensured the American national anthem was played four times in quick succession for the crowd of 9,000 spectators.
Ligety's superiority was helped by his ability to adapt best to equipment changes introduced for this season with longer and stiffer skis meant to make the discipline safer.
Some had predicted it would also make the GS races less exciting, but Ligety defied those critics by delivering some of the most dynamic skiing seen all season in any discipline.
"I had some of the most unbelievable runs this year," said Ligety, who collected a trophy this week when fellow skiers voted his first-leg performance at Alta Badia, Italy, in December as the most exciting all season. "I was able to keep it going the whole year."
A buzz went around the knowledgeable Swiss fans when Ligety was in the start gate, and he was warmly applauded after completing each run
"It's cool that people appreciate that," Ligety said. "It's becoming more exciting, especially with guys like Hirscher and Pinturault being so good at it. There are good story lines and more rivalries."
Ligety acknowledged that he must get closer to his main rivals in slalom, which had nine scheduled World Cup events this season, to challenge for the overall title.
Hirscher, a two-time overall champion at 24, said Ligety had told him it was "a big goal."
"If he feels more confident in slalom, he can win for sure the overall World Cup," Hirscher said.