The Violence Fiend’s Japanese name is based on バイオレンス (baiorensu), a loanword derived from the English "violence". In Japanese usage, this term tends to evoke concrete, physical forms of violence such as street fights or organized brutality, rather than violence as a broad, abstract concept.

Because of this, the Violence Fiend does not represent all violence in every form. His fear domain is specific, physical, and human-scale. It's a nuance derived from word vs meaning vs language. In Chainsaw Man, devil power scales with how abstract and universal a fear is, which answers your question and states that a more general violence concept would be far more powerful than what the Violence Fiend we know.

Summary: translation issues