O K2 (2016)

In both the ML get the job to protect the FL. The first as soldiere the other is ex-soldiere.
In both dramas, FL and ML get to know each other better and fall in love. But there are a few obstacles in there way to happiness.

If you like bodyguard dramas watch both.

They both deal with an MC who was previously involved with the military and is now trying to live a normal life as they deal with a traumatizing death in their past. They are then dragged back into fighting through meeting new people. Both shows also have awesome fight scene. But The fiery priest does have more humor then k2. Both are good shows.

Both Dramas ML are top elite agent in their field (TV - NIS agent , K2 - Soldier)
Due to some reasons ML gets rogue/disappeared due to conspiracy
Full of Action, Mystery, Thriller which will keep you on the edge to watch what happens next
If you like the veil I suggest to watch The K2 as well

In both kdramas the theme is used: Money is power.
Both deal with corruption and murder. Somehow Signal ended for me where the story of The K2 might start.
2 of the best kdramas that got released in 2016
definitely a must watch!

Both are action dramas that also involve romance, and both male leads help, save or rescue the female lead.