Passionate fans help to make football the unique sport it is. The support of the faithful, unlike many sports, does not stop once the final whistle blows; it is something lived and professed throughout one's life, showing a commitment that at times borders on the obsessive.
Unfortunately, in many areas of the globe this fanaticism often can spill over into violence. The trend is exacerbated by the presence of organised fans, often dubbed "hooligans," whose interest in the sport seems to take a secondary standing to their love of fighting and causing mayhem.
The teams listed in this article have all suffered serious problems with violence in the last 10 years, to the point where fans have lost their lives as a result of the actions of others.
Anyone who has been to Newell's' stadium in Rosario will tell you that it is an extremely intimidating place to visit thanks to the passion of local fans. Much of the violence in recent years, however, has actually taken place between supporters of the Lepra.
Argentine hooligan firms, or Barra Bravas, often draw extensive economic benefits from clubs, selling merchandising, match tickets and organising parking outside the stadiums. When part of the firm decides it wants a bigger cut, things can get very bloody.
In 2010, 14-year-old Walter Caceres was shot and killed when a bus carrying Newell's fans and part of the barra was ambushed by a rival faction (La Capital). Just one month later, hooligan heavyweight Roberto "Pimpi" Caminos was executed in a drive-by style shooting in the early hours of the morning, his body dumped outside a local hospital (26 Noticias).
Football hooliganism in Poland is a well-established issue, and most major teams have their own firms ready to cause mayhem in the name of the shirt. Few, however, boast the same infamous reputation of Wisla Krakow's firm, the Biala Gwiazda (White Star).
The hooligans of the club were implicated in the 2011 slaying of Tomasz C, second-in-command, according to the Krakow Post, of rival club Cracovia's own violent fraction. Tomasz was set upon by around 12 men armed with machetes and baseball bats in a clearly orchestrated ambush, one of several deadly attacks that have been perpetrated by both teams' fans.
The reigning world champions are one of the biggest, most widely supported football clubs on the planet. Similar to many Brazilian and South American teams, however, the Timao have long suffered the effects of organised hooligans inside the institution.
Earlier this year the Sao Paulo outfit were ordered to play Copa Libertadores fixtures behind closed doors, after a match against Bolivians San Jose took a tragic twist. The Mirror reports how 14-year-old Kevin Beltran was hit by a flare thrown from the away stand by Corinthians fans, provoking a brain haemorrage and the death of the teenager.
In a phenomenon that coincided with the fall of communism and the resulting surge in far-right, neo-nazi politics, Eastern Europe and the Balkans has become a hotbed of violent hooligan activity. Serbia's Partizan Belgrade are no exception.
In 2008, as reported by Reuters, a man was shot dead in what appeared to be an organised battle between hooligans from Partizan and Novi Sad. Just one year later there was more fatal violence; Toulouse fan Brice Taton was beaten to death when supporters of the French club were ambushed in a Belgrade bar prior to a Europa League clash.
Italy's organised football fans, the infamous Ultras, are similar to their counterparts in South America for the influence and reach they hold over football clubs in the nation. Capital clubs Roma and Lazio are both known for their fearsome hooligans, as are Sicilian institution Catania.
Football across Italy was suspended in 2007 due to a death provoked by Catania supporters following an island derby against Palermo. Police officer Filippo Raciti lost his life trying to control a riot after being hit with an explosive device thrown into his vehicle and receiving several blunt traumas, as reported by the New York Times.
Situated in the Peruvian capital of Lima, Universitario alongside Alianza are one of the traditional powers of the nation's football scene. A fierce rivalry has grown up between the two neighbours, which has the potential to end in deadly consequences.
The last death did not happen in the rough-and-tumble of the terraces, but in a private box of Universitario's Estadio Monumental. Alianza fan Walter Oyarce was watching a 2011 derby when he and friends were jumped by home hooligans.
The thugs, according to the Daily Mail, ended up pushng the 23 year old off the edge of the box. Oyarce initially survived the 30 ft fall onto solid concrete but died of his injuries on the way to hospital.
"Welcome to Hell," read the famous banner in Galatasaray's old Ali Sami Yen stadium to greet European visitors. Fans of the Istanbul giants have long been considered as some of the most passionate, and violent, in the world.
A catalogue of violence accompanies the club and its supporters, events which on more than one occasion have been fatal. In 2000, two Leeds United fans were stabbed to death in violent clashes ahead of a UEFA Cup meeting between the English and Turkish teams. And earlier this year, a knife was again the weapon of choice to murder a Fenerbahce sympathiser, 20-year-old Burak Yildirim.
One of Colombia's biggest, most successful clubs have suffered the scourge of hooliganism for years. For a team that in the 1980s was partially bankrolled by notorious drug baron Pablo Escobar, criminal activity has never been too far away from the venerable Medellin institution.
In 2012, as reported by FoxSports (in Spanish), running battles between Nacional fans and rivals Independiente Medellin following a derby left one fan dead from a gunshot in the head, as well as nine injured and 315 arrested.
They are also not afraid to fight amongst themselves; a new casualty was recorded in 2013, knifed to death during an apparently pre-organised battle between rival hooligan factions according to RCN (in Spanish).
The Buenos Aires giants, like compatriots Newell's, have also suffered violence from within the club. Two feuding factions are battling for control of the multi-million peso business that is being head of the Xeneize barra, leaving a deadly impression on the club.
Prior to a preseason friendly against San Lorenzo in July of this year, the two rivals staged a shootout outside the stadium which left two barra members dead (Buenos Aires Herald). The event was instrumental in the decision to maintain a ban on away supporters throughout Argentine football, but tensions in the Bombonera remain stretched to breaking point.
Before last year few people would have been aware of Port Said club Al-Masry, or Egyptian football in general. But in January 2012 the team put its name in public consciousness in the worst manner possible.
Celebrating a victory against Cairo powerhouses Al-Ahly, Masry fans celebrated by going on the rampage, as reported by USA Today. Away players were chased off the field by supporters, who then turned their attention to those in the stands; leading to clashes and a stampede that left 74 people dead and 248 injured.
Opposition politicians alleged that police had allowed Ahly supporters to enter with knives and other weapons and did not intervene once trouble started, contributing to the most deadly football incident since 1996.