While so often the world of fighting and combat sports is based around respect and a competitive edge, sometimes there's no better sight than seeing two fighters who have nothing but pure and unadulterated hatred for one another.
Whether it's merely faux hatred for the purpose of raising intrigue and selling a fight, or a case of genuinely detesting another person to the point of it being far more than just another fight, heated rivalries sell PPVs and get people through the gate.
It's been said over the years that controversy creates cash, and seeing somebody mock an entire country or discuss their plans to actually kill an opponent is most definitely controversial - yet these instances have also brought in some mega PPV hauls and ticket sales.
For the UFC, the very nature of the fight game means that great rivalries are so often a key component of having a successful company on a variety of different fronts. And that's why so many of the UFC's boom periods and surges in popularity have coincided with some truly legendary rivalries.
With that in mind then, here are ten of the most heated and vitriolic rivalries in the history of the Ultimate Fighting Championship.