So this is UCL's save percentage this season so far (November 11th, 2023): https://fbref.com/en/comps/8/keepers/Champions-League-Stats Yashin had 80% in the 1966 World Cup (there is no data from other World Cups), Maier 86% in 74, Banks 88% in 66, Taffarel 80% in 90, Cech 71% in 06, Zoff 82% in 82, Felix 81% in 70 Neuer 87% in 2010, Buffon 93% in 06, Kahn 87% in 02, Fillol 90% in 78, Schumacher 76% in 86 Dasayev 86% in 82 Preud'homme 85% in 94 Barthez 86% in 98 Marcos 86% in 02 Casillas 88% in 10 Ilgner 62% in 90 Pumpido 72% in 86 Lloris 75% in 10 and 14 Gilmar 63% in 66 (there is no data from World Cups before 66, the two he won in 58 and 62 have no data) So among the world champion goalkeepers (and other historic players like cech and yashin), the biggest save record is from Buffon, according to sofascore
Others great keepers: Leão 90% in 78 Dida 90% in 06 Van Der Sar 89% in 06 Martinez 47% in 22 Courtouis 82% in 18 and 22 Goychochea 82% in 90 Higuita 82% in 90 Chilavert 91% in 98 Shilton 91% in 82 Valdir Perez 56% in 82 Mazurkiewicz 81% in 66 Muslera 77% in 18 Vitor Baia 71% in 02 Julio Cesar 71% in 06 Alisson Becker 71% in 22 Peter Schmeichel 73% in 98 Jan Jongbloed 80% in 74 Zubizaretta 83% in 86 e 98 Jans Lehman 69% in 06 Jorge Campos 80% in 94 Ochoa 81% in 18 Tim Howard 82% in 14 Navas 91% in 14 Zenga 92% in 90 Meola 86% in 94 Szczęsny 82% in 22 curiously historically low: Armani 29% in 18 De Gea 14% in 18 90% or more Buffon 93% in 06 Zenga 92% in 90 Navas 91% in 14 Chilavert 91% in 98 Shilton 91% in 82 Leão 90% in 78 Dida 90% in 06 Fillol 90% in 78