Is a full grown hippo so big and bad that it can casually walk up to a group of lions or tigers, look at each one and just sit right in the middle of them without them even attempting to attack it?

Annoyingly, yes and no.

Sometimes hippos actually do this. They come out of the water and challenge lions as if to say, “I dare you to try me. I will bite you in half” ( & sort of have–i could include some video but it’s quite disturbing.)

However, lions know how to hunt. They know their advantage lies when they have surprise, not when hippos have already seen them to the point to consider challenging them. Lions typically kill hippos at night or in the wee hours of the morning when they are attempting to make it back to their water hole or river.

For those who aren’t aware, hippos leave their watery refuge every night and enter the plains to feed. They’re incredibly vulnerable bc they don’t have keen night vision. They just follow the same trails they’ve previously taken.

Lions anticipate this. They recognize they’re blind and vulnerable at night and this is when they herd them away from their water holes/river and further Into the savannah. By day break, the hippo are tired and beginning to overheat/dehydrate. It won’t be long before the sun does the work for the lions.

I’ve personally known and experienced lions who are smart enough to intentionally do this. At first, it looks like their night hunt has failed on the hippo, when in reality they are Intentionally waiting for the sun to bake the life out of the hippos. They’re the smartest big cat for a reason.

Above: male lions in their nomadic phase often become hippo hunting specialists

So, yes, hippos will come out of their watery hole and challenge lions…but, those same hippos are later targeted and killed.

With this all said, the vast majority of hippos targeted by lions are youngsters. But, they will take advantage of any opportunity that presents itself, adult or otherwise. To say that lions can’t or don’t take down adult hippos is false…granted, it isn’t their preferred prey.

[Lastly…hippos don’t cross paths with tigers as your questions suggest, they don’t inhabit the same terrain.]