West Germany 1-2 Algeria — Spain 1982

Algeria's 2-1 victory over West Germany in 1982 marked the first World Cup win by an African team against a European powerhouse. Rabah Madjer and Djamel Zidane scored within 10 minutes of each other to overturn Karl-Heinz Rummenigge's opener. The Germans then colluded with Austria in the infamous 'Disgrace of Gijón' to eliminate Algeria on goal difference, prompting FIFA to mandate simultaneous final group matches. Algeria's upset is 25% more significant than the average because it directly changed World Cup rules. It falls behind #3 Senegal vs. France due to France's status as simultaneous world and European champion, a rarer achievement than West Germany's single World Cup title at the time.