While related by root, "bestialize" is a verb describing a process of degradation, whereas "bestiality" refers to specific sexual acts between humans and animals.
It is a formal term. In everyday conversation, people are more likely to use "dehumanize" or "brutalize" to convey the same meaning. bestialize
To reduce to the state of a beast; to brutalize or deprave. Common Contexts: While related by root, "bestialize" is a verb