3. Montreal Canadiens
Hockey atmosphere in Canada the among fan bases is unmatched. The Senators' hatred for the Montreal Canadiens will always be there.
One thing that immediately goes into the rivalry is the amount of Canadiens fans that travel to Ottawa when the Canadiens play at Canadian Tire Centre. Under 2.5 hours separate the two cities apart. Ottawa having over 40 percent of the population speak French also intensifies the rivalry because Quebec's main language is French.
It might sound shocking for some fans, but the Senators and Canadiens have only played each other in the Stanley Cup Playoffs twice. Both times were in the first round of the playoffs in 2013 and 2015.
In 2013, the Senators entered the playoffs as the seventh seed in the East against the Canadiens, who were the second seed. The Senators upset the Canadiens in five games. In the series-clinching win in Game 5 in Montreal, the Senators laid an embarrassing 6-1 win against the Canadiens.
Unfortunately for the Senators in 2015, they fell in six games to the Canadiens. The first three games of the series Ottawa lost by one goal. Two of the losses came in overtime. The Senators won the next two games to force a Game 6 back in Ottawa, but were shutout 2-0 to lose the series.
Every NHL team's fan base in Canada will have a hatred for the Canadiens. The Senators are one of those fan bases that will have hatred toward the Canadiens.