"Deadpool and Black Panther have surprisingly little history with each other for two such famous characters. Even back when Christopher Priest was writing both titles and had them cross over, it was during a period where Erik Killmonger had temporarily taken over as Black Panther (in a story that was partially adapted for the Black Panther film), so while Deadpool fought against a Black Panther, it was not T’Challa. They recently did have a confrontation during the Civil War II crossover event, when Deadpool infiltrated the Ultimates’ headquarters in an attempt to kill the prognosticating Inhuman Ulysses. He had changed his mind by the time Black Panther discovered him and then soundly defeated him and threw him out of their headquarters…literally. This will be their first fight since." Taken from the article.
I think the writer left out the part where T'Challa hired Deadpool during Doomwar. But who cares.