I can add two methods used by Africans to kill Elephants.
The Pygmy hunters would find a trail through a wooded area that they knew Elephant used, they dug a hole in the middle of the trail, the hunter would lay in the hole which he or a companion would cover carefully.
When the Elephant strolled down the trail the hunter would strike upwards with a slim spear head to pierce the heart then try to get out from under before it fell or could grab him with its trunk.
Another method involved running at an Elephant as it passed the hunters place of concealment, and slashing a hind leg with a hatchet.
A deep hatchet wound would imobilise or at least slow down the Elephant and it would bleed out fairly quickly.
As for Black Bear their brain is not situated in the same orientation in the skull as other bears. The Black Bear Brain sits much lower and farther forwards in the skull, due to its specialized sense of smell. The olfactory nerves run straight to the brain from its large nasal passages.
The best way to hit a Black bear in the brain is to fire into its open mouth or through the nose. Bullets can sometimes bounce off its fore head, and from the side its jaw attachment points are pretty thick and can deflect a bullet.
Not sure if a shot through the ear would actually reach the brain, or just waste energy in bone.
PS
The Grizzly Bear Old Moses was found to have three healed over bullets in his brain. They were .38-55 bullets fired straight into his maw by one of his victims. They had found the shattered rifle and skull of that victim decades earlier. Old Moses had caught the man, who was a professional hunter, in his bed roll and the hunter got off three shots from his lever action before the Bear came down on him like the wath of God.
Old Moses had more than one hundred healed bullet wounds including musket balls.