The phrase "meaner than a junkyard dog" is often used to describe someone who is extremely aggressive or hostile. However, there are many other phrases that can be used to convey a similar idea. Some examples include "as vicious as a rattlesnake," "more ferocious than a hungry lion," or "as dangerous as a cornered bear." These phrases all use animals to convey the idea of someone being aggressive and threatening. Other phrases might use different comparisons, such as "more ruthless than a corporate executive" or "more cutthroat than a professional athlete." Ultimately, there are many ways to convey the idea of someone being excessively mean or hostile, each with its own unique nuance and connotation.