What are the deadliest rivalries in football?
The most heated rivalries are always when there is an underlying political or religious element to the football clubs.
Zagreb and Belgrade for instance, who had previously been fighting each other in a civil war.
Rangers and Celtic, fuelled by sectarianism and the political conflict in Northern Ireland. Celtic fans sing songs glorifying the IRA and Rangers fans sing about Bobby Sands dying from hunger strike.
England-Argentina, England-German, Scotland-england...