The star of the show here is Chalamet, who shows up 15 minutes into the narrative, wearing his hair floppy and a chip on his shoulder as the wayward Prince Hal. He's been ignoring the wars being fought by the likes of Hotspur (Tom Glynn-Carney) on behalf of his father, Henry IV (Ben Mendelsohn, pleasingly hammy), by partying his days away. But, as is typical with kings, they eventually die, and Hal must eventually assume the crown and get a really crappy bowl cut.
It's a tale as old as monarchy, but Michôd and Edgerton never find anything new to say about a young man rising to power. In the absence of actual character development, Hal becomes a largely passive figure, deferring to others for counsel, torn between the whispers in his ears. It's a disservice to Chalamet, the internet heartthrob who owned the 2017 movie season with Call Me By Your Name and Lady Bird. Chalamet's breakout performances are opposing portraits of teenage lust. Elio in Call Me By Your Name conveys all the awkward obsession of first love; Kyle in Lady Bird is the easily identifiable self-interested, bass-playing toolbag of nearly everyone's youth. He's done admirable work in the years since then, but nothing has really capitalized on the charisma that birthed his intense fanbase. The King doesn't change that. (Just stay tuned for Little Women, out later this year.)
Chalamet is fine as Hal. He settles into the stately accent well, and ultimately assumes the posture of a knowing leader, giving a bastardized version of Shakespeare's St. Crispin's Day speech. But he's hamstrung by the inertia of the material, his muted performance blending into the muddy tones of the landscapes. (He does speak French at times, so at least there's that.)
All this is to say that, yes, Pattinson really is the only reason to watch The King. In a film that takes itself so SO seriously, he decided to have a little fun. His performance as the Dauphin is not necessarily what you'd call "good." In fact, it has actively bad elements -- like that accent, for one. But it is an inspired bit of pageantry that The King desperately needs.