A bear. Bears (especially Brown Bears) are much larger and stronger than a lion, and would overwhelm and crush it.
Lion
The atlas bear would win.
The grizzly bear would probably win
polar bear
The giant black bear would win, but it would be injured.
Neither as the black bear is from North America and the lion from Africa and Asia. They never meet in nature.
Lion would be killed. Grizzly bear would be more powerful and stronger.
The lion would be killed. A polar bear would be enormous and powerful. One swipe of paw can shatter the lion's skull.
a lion mostly
Probably the black bear.
It depends on who is bigger. If the black bear happened to kill the lion, the black bear would get badly injured.
a polerbear would win because it is stronger and has stronger and sharper teeth and the lion will be helpless