Sure, it isn't a challenge, but unlike a GALACTIC EMPIRE, the idea that blowing up a goddamn planet-destroying-planet isn't a huge hit to the might of a relatively small Imperial-remnant nuisance (as far as the Republic was concerned) is pushing it. If the current incarnation of the new Republic isn't at total war against them over the destruction of the Senate and temporary capital by the time we pick up in The Last Jedi they'll be seriously stretching credibility.