In the book, Of Mice and Men, how is Lennie shown as energetically forceful?

When he feels the red dress of the girl in the previous town to the new town he and George travel to. Along with this, he kills multiple mice as he wants to pet them. He also kills a dog because he wanted to pet IT. Another example, when he kills Curley's wife, after wanting to feel her hair, but grabs onto her neck and when she tries to pull away he breaks her neck.