Responses
Deadlock, but it has a little romance
there is some in female lead
https://www.mangago.zone/home/mangalist/1145002/
I would highly recommend Mercenary Enrollment!
It involves MC used to be trained as a mercenary and you can see him killing mercilessly in the past. There will be a high school setting though in present time but he will still be a baddass fighting off school gangsters.
Any stories that are actions no romance not fantasy,bonus if have guns knifes blood black market