Four stars. Rated R. 119 minutes. In a recent interview, the star of “Deadpool 2” joked that his character probably wouldn’t like the actor who plays him very much, saying, “I feel like Deadpool can’t stand Ryan Reynolds.” And he’s probably right. There is, in fact, a scene in the new movie in which the foulmouthed contract killer with a heart of gold — and here I’m talking about Deadpool, not Reynolds — actually appears to kill the Canadian-born movie star, adding a snarky “You’re welcome, Canada” as he violently does him in. But what would Deadpool think of the movie? That question, however rhetorical, encapsulates the challenge inherent in reviewing this new Marvel sequel.