Words that mean to make something less wild are to tameor to domesticate.
He behaved like a wild animal.
He was the very personification of the boy in the book called Where The Wild Things Are. That is a good example because the word means to act or show characteristics of something nonhuman.
Tame or domesticated.
How a wild animal acts
Coyote, prairie wolf...
Diminish
Heal
ameliorate, ease, soothe, deaden...
Allay, Abate
The prefix "de-" means to reverse the action or make something less or smaller. For example, "deflate" means to make something smaller by removing air.
Destabilize means to make something less steady or less secure. It's the opposite of stabilize, causing disruption or uncertainty.
Tame.
"Weaker" means less powerful.
While the word is much less common in everyday speech, the word "habilitate" means "to make fit" or "to become suitable for certain conditions". Therefore, to rehabilitate means "to make fit (or suitable) again".
insane.
Escapade.
The word feros in Latin means the inflection of ferus. Ferus is a Latin word that means a wild animal, some adjectives are wild or savage.