I like Val McDermid’s earlier books, especially the Kate Brannigan series - so if you like her writing them and the Lindsay Gordon series are worth hunting out.
I’d second Tess Gerritsen.
The books that might be closest in style to Val McDermid’s are Mo Hayder, starting with Birdman. Warning though - I like my mysteries very dark, but I found Birdman deeply unsettling.
Elizabeth George is worth a try. I find her aristocratic detective and working class chip-on-shoulder partner verging in caricature, but that settles down a bit after the first book. And if you do like her, you’ll have a substantial chunk of reading to get through.
A personal favourite of mine are the Dalziel and Pascoe novels by Reginald Hill. Don’t let the TV series put you off, the novels are deeply quirky and complex. I think On Beulah Height might be one of the best crime novels I’ve read.
Also Tami Hoag’s Kovac and Liska series are good. Hoag writes great dialogue.
And not quite a detective partnership, but JD Robb’s In Death series. I think she phoned the last couple in, but super entertaining, if slick, up til then.
Jack Kerley’s Carson Ryder books are gory fun.
Not a detective pairing, but if you enjoy really dark mysteries, John Connolly’s Charlie Parker books are truly creepy. I love him, he’s such a good writer, but I wouldn’t read them in the dark.
Rather than a detective pairing, a team, Cody McFadyen’s Smoky Barrett books. Gripping, and very intense.
Worth checking out Karin Slaughter, Michael Connolly and Ian Rankin.