Como dizer "em pessoa" em inglês

The king in person. It could be also metaphorically:
See this incredible tribute show and relive the excitement of having seen "The King" in person during the height of his career in Vegas of the early 70s.

In the flesh/in flesh and blood. (but be careful, they are less used and it depends on context.)

And the "king himself":
Scarcely could he tell, so out of breath with haste and transported was he, that the King himself and the Count were coming. “Yes, the King! The King in person!” repeated he, “publicly coming!
Source: the book Caroline of Lichtfield by Isabelle de Montolieu, edited by By Laura Kirkley.

Ah, one example here, so you will see how it works in a sentence:

When Wycherley became severely ill in 1678 the king himself visited him at his lodgings and then gave him £500 to travel to the health resort of Montepellier, in France.

Source: Encyclopedia of British Writers, 16th, 17th, and 18th Centuries

If you (or the author) wanted to add some more dramatic effect to the sentence he could redo it into "When Wycherley became severely ill in 1678 the king himself - no less - visited him at his lodgings and then gave him £500 to travel to the health resort of Montepellier, in France.
The particle "no less" would add somehow a "surprise" ring to the narrative.