Have you tried the currently-airing Kill It? it finishes this week, so there's not a lot of waiting, but the ML was trained to kill people (and he's good at it.) There isn't really much romance and whilst the chemistry is good, I feel like if it was developed further, it would detract from the story. It's fun, it's good at setting up atmosphere and there's crime/mystery. The action scenes are particularly good.
You may also like The K2. I wasn't enamoured, but that's personal opinion, as a lot of people hold it some high regard. There's action and romance, with a mysterious and capable lead.
I also noticed that you have Healer in your PTW list. It's a must-watch and though not without it's faults, I loved it. An elite, highly trained and morally grey (he's a thief) protagonist, with mystery, action and satisfying romance.
