Black bears are the most “cowardly”, but all three will fuck you up to protect their young
Eh, not really… Black bear cubs are quite capable of climbing trees, the mother will definitely make her displeasure known to you, but it’s mainly for show.
Source: I once unwittingly startled a mama black bear and her cubs, ended up falling flat on my back so I was quite vulnerable, she could have easily torn me apart if she wanted to, but she just charged at me, stopped about 6 feet away grumbling, stomped the ground, and clacked her teeth at me. The cubs were up their trees faster than squirrels.