Short answers, pulled from the story.
The Akron Pros claimed the first championship of what would become the National Football League. They finished an eight-game season with zero losses and three ties. The league executive committee denied petitions from the Buffalo All-Americans and Decatur Staleys for a shared title.
The league held its first official playoff game on the 4th of December 1932. Severe winter conditions forced organizers to move the match indoors at Chicago Stadium. The Chicago Bears defeated the Portsmouth Spartans by a score of nine to zero.
Cleveland Browns quarterback Otto Graham led his team to four consecutive championships between 1946 and 1949. The Browns completed an entire undefeated season in 1948 with twenty-four wins and no losses or ties. Their records remain excluded from official NFL record books despite their dominance.
The Green Bay Packers won the first two matches against Kansas City Chiefs and Oakland Raiders. These contests preceded the modern Super Bowl name which was officially adopted in 1968. The last two victories went to the New York Jets and Kansas City Chiefs of the AFL.
The Miami Dolphins played an undefeated season in 1972 but lost their AFC Championship Game due to home field advantage rules. Home field advantage remained determined by divisional rotation rather than regular season records until 1975. Tie games began counting as half a win and half a loss from 1972 onward.