The Main Categories That Make a Tree Dangerous are:

Decay

Three shelves of white fungus growing on a tree trunk in a forest.

Splitting

Close-up of a tree trunk with a deep crack and damaged bark

Overgrown

A tree struck by lightning during a storm, with visible fire and smoke at the point of impact.

Disease

A large tree in a park with bare branches and green leaves growing on the trunk, under a sky at sunset or sunrise.