I would say the most passionate fans are probably in Hamilton nowadays. Its a blue collar city that feels undervalued and underappreciated in Canadian society, and people would turn out to support their team, which would be by far the biggest act in town. The fact that Hamilton has been recently successful and considered somewhat villainous by the rest of the league is also a boost to potential fan support, as it further entrenches an "us against the world" mentality amongst the fanbase.