The lion-hyena, two species that are evenly matched in size, strength, and power.
This isn't quite accurate; spotted hyenas and cheetahs are about the
same mass (40-86 kg and 35-72 kg respectively) while hyenas and lions
are extremely different in size (40-86 kg and 82-120 kg (females),
respectively). Both hyenas and lions get away with stealing food from
cheetahs not because the cheetahs are too small to fight back but rather
because they have a pathological fear of fighting. They won't do it,
even if they have a good chance of winning. Hyenas and lions face off
not because they're matched in size and strength but rather because the
hyaenas run in larger packs and are extremely aggressive (spotted
hyenas, mind you; totally different story with the smaller striped and
brown hyenas).
In a one-on-one battle even the largest hyena would not take on a ioness for to long as not only is the lioness physically stronger, but unlike the hyena is equipped with an arsenal of strong, very sharp claws. The fact that hyenas out number lionesses at a kill and therefor have a chance to attack from behind is what puts them on a par.