Here are some examples:
* Soften: This is the most common and straightforward way to express the action of making something softer.
* Harden: This is the opposite of soften, and it uses the same suffix "-en."
* Loosen: This also uses the suffix "-en" to express the act of making something looser.
While "-ify" is a common suffix for verbs, it's less used for "soften" in standard English.