Tigers and especially lions are somewhat easy, not to domesticate per se but to befriend. I wouldn't really call this a hack the way domesticating dogs was a hack--they just seem willing to occasionally befriend humans the same way ordinary cats do.
Tigers and lions are very confident apex predators, so they don't really have the vicious instinct or the intense fear response that some animals have. So they don't deliberately attack humans. By contrast, leopards and jaguars will kill you out of sheer viciousness, bears will attack you if they feel threatened, and polar bears will attack you because they are hungry and you are made of meat.
The main danger with tigers and lions is that they don't really understand how fragile humans are, so they might accidentally kill or maim you, which happened to Roy.
Tigers and lions are very confident apex predators, so they don't really have the vicious instinct or the intense fear response that some animals have. So they don't deliberately attack humans. By contrast, leopards and jaguars will kill you out of sheer viciousness, bears will attack you if they feel threatened, and polar bears will attack you because they are hungry and you are made of meat.
The main danger with tigers and lions is that they don't really understand how fragile humans are, so they might accidentally kill or maim you, which happened to Roy.