The study - conducted by betting tips and predictions website Nostrabet.com - analysed every tournament since FIFA's expansion to 32 teams for the 1998 edition, to find out which winner had the toughest path to the trophy.
The research used FIFA’s ranking points, creating indexes based on each team’s points totals at the start of every tournament.
The number one team scored a maximum 100 points, and all other nations’ points totals were converted to scores out of 100 relative to their ranking.
It found that Italy’s 2006 win was achieved against teams with the highest combined ranking points than in any of the tournament's other versions.
Marcello Lippi's men were placed in a group with Ghana, the USA and the Czech Republic, who were the second-ranked side in the world before the tournament.
After sealing top spot in Group E, Italy battled past Australia and Ukraine before knocking out Germany after extra time in the semi-finals.
The Azzurri then managed to overcome France in the final via a penalty shootout, to seal their fourth World Cup title and first in 24 years.
The combined ranking points of Italy’s opponents came to a total of 608, which was the highest value of the six champions analysed between 1998 and 2018.
In second, France’s win on home soil in 1998 was found to be the next toughest campaign.
Led by Aime Jacquet, they won all three group games against Denmark, South Africa and Saudi Arabia before dispatching Paraguay, Italy and Croatia in the knockout stage.
A Zinedine Zidane-inspired Les Blues then cruised past Brazil 3-0 in the final, taking their opponents' ranking scores to 599 overall.
Brazil’s title win in South Korea and Japan in 2002 was ranked as the third most difficult.
They breezed through their group against Turkey, China and Costa Rica, then defeated Belgium, England and Turkey to reach the final against Germany.
Two goals from Ronaldo sealed the Seleção's fifth World Cup crown, with their opposition points totalling 770.
Of the six World Cups measured, Spain’s win in South Africa 2010 saw them face teams with the lowest combined ranking points of 539.
France’s triumph in the most recent World Cup in 2018 saw them placed fifth out of six in terms of difficulty (551), while Germany’s 2014 win in Brazil was fourth on the list (555).
