Jack Reacher, or just Reacher, as everyone (including his mother!) calls him, is played by Alan Ritchson, who is perhaps best known for his roles on Smallville where he played Aquaman/Arthur Curry, and as Thad Castle on Blue Mountain State.
Ritchson, an already large human, bulked up and gained over 30 pounds for the role. He aimed to look more like the Reacher envisioned by Child in the novels rather than the version that Tom Cruise embodied in the two film adaptations where he portrayed the character. In being faithful to the character in the books, Ritchson succeeds wholeheartedly.
The dialogue is extremely clumsy and, as you probably guessed, riddled with clichés, but Ritchson can maneuver past it and deliver a solid performance.
However, when the character itself isn't great to begin with, the viewer's first instinct might be to blame the actor rather than the writer. In the case of Reacher, that is unfair to Ritchson and Lee Child.
Ritchson is particularly great in the action scenes, delivering the moves with shocking brutality and force, which I'm sure was met with Child's approval.
Word of warning for those who are a little squeamish: Reacher is a bloody and brutal show with plenty of bone-crunching and killing to be found.