What are some prefixes for not safe?

It's difficult to provide prefixes for "not safe" directly, as it's more of a concept than a word. However, depending on the context, you could use these prefixes to convey a similar meaning:

For "not safe for work" (NSFW):

* Un-: Unsuitable, Unacceptable, Unprofessional, Unorthodox

* In-: Inappropriate, Inadvisable, Insecure

* Non-: Non-work-appropriate, Non-family-friendly

For "not safe for children" (NSFC):

* Un-: Unhealthy, Unwholesome, Unpleasant, Unsettling

* In-: Inappropriate, Inhumane, Inconsiderate, Inaccurate

* Non-: Non-child-friendly, Non-educational, Non-constructive

For "not safe for general viewing" (NSGV):

* Un-: Undesirable, Unpleasant, Unsettling, Unconventional

* In-: Inoffensive, Inaccurate, Incoherent, Incomprehensible

* Non-: Non-general-audience, Non-mainstream, Non-public-friendly

For "not safe for everyone" (NSE):

* Un-: Universal, Unacceptable, Unconventional, Unconventional

* In-: Inclusive, Inconsiderate, Incoherent, Incomprehensible

* Non-: Non-inclusive, Non-universal, Non-mainstream

Ultimately, the best prefix will depend on the specific context and what you are trying to communicate.