1978: The whole 1978 Argentina World Cup was a farse assembled by the dictators. Brazil didn't lose any game at all and was desquilified when Argentina, who needed to beat Peru for 6 goals, did it. The goalkeeper for Peru was Argentina-born, anyway. Brazil had to move thousand of miles inside Argentina for the games, while Argentina played almost in the same place always.
1986: Maradonna scored two non-valid goals, including one with his hand (the famous "Mano de Dios").
1990: Argentina poisoned the brazillian player's water bottles for their match against Brazil. After years of denial, Maradonna and other members of the argentinean team confirmed this.
1994: Maradonna was caught on the dopping exam.
They usually play very dirty. Injure oponnents when the referee is not watching, simulate faults and injuries for their benefit, stall the game, throw several balls into the field to stop the plays (like they did today).