The term "paper tiger" refers to something that appears to be strong and threatening but actually has no real power or substance. If you need alternatives to this phrase, you could try using "faux intimidator," "illusory menace," or "pretend predator." Other options include "hollow threat," "phantom foe," or "sham challenger." Another way to convey the concept of a paper tiger is to use the idiom "all bark and no bite" or the term "toothless tiger." These synonyms can help add variety and interest to your writing while still conveying the same idea as "paper tiger".