From what I know a pack of African wild dogs will sometimes take down a lion, course we're talking about a pack of dogs, not just two.
The only thing a grizzly bear will run from, is a pack of dogs....or wolves. Any sort of wild dog pack, is a terrible opponent for any animal to face.
When I was going to college I worked at the St Louis Zoo as an announcer for the summer animal shows they had. During one memorable lion and tiger show I witnessed a fight between four adult male lions and one male tiger. Wildest thing I have ever seen. When it was over all the lions were severely injured. Two had to be taken out of the show for the rest of the season. Two more limped badly after that. The tiger was a little bloody...couldn't tell too well. It was probably lion blood. That fight didn't end till the trainer, who was in the ring all the time, hit the tiger over the head with a massive pole. The tiger who was chomping a lion at the time, just looked up, then jumped back on his little stand. Heh.
While all this was going on, I was saying, "don't worry folks, everything is under control". Ha. You never heard such roaring...people screaming, mass panic. How I spent my summer.
The most dangerous show was the elephant show...when those animals lost it, everybody was in danger.
They also had a chimp show...cute little chimps huh? I saw one go crazy once. Not very big at all, maybe 40 lbs. It took four men to subdue it.