Polar bears eat walruses and they have thicc ass hides too, i assumed they could do something about the hippo hide?
Most polar bears don't prey on actual bull walruses. The latter of which actually put up a good fight. Their best bet is to prey on juveniles or females and even then a successful kill isn't guaranteed
most of the time.
And what about siberian tigers? These things can take down brown bears.
Siberian tigers do prey on brown bears but again, iirc, they mostly prey on the younger/ the sick/ female bears that are hibernating. A full sized Kamchatka bear would pose a great threat to a male Siberian tiger. The result of these two would likely just be to avoid each other. Injury isn't something they are willing to go after especially if food is already scarce. They are better off hunting smaller animals.
While the hippos jaw is powerfull, it lack maneuverability imo,tiger is way more agile and the bear is more polyvalant as it can use its legs to roll the hippo over.
That is assuming if the tiger has the jump on the hippo first. And even then, the hippo is too damn large for a Siberian or a brown bear to tackle. The hippo either needs to be a weak, old, young, and maybe a female version for it to happen.
Hippo's maneuverability isn't as good but to think that a tiger will strafe left and right and pounce on him quite easily is foolish. All the hippo needs to do is turn towards the predator's direction. Mathematically speaking, it is way easier.
I think a lot of people sleep on herbivores. I personally think even an Iberian bull would beat the shit out of a tiger or a lion.
P.S. you should make more animal fight threads. I love discussing them.