For me, Carter feels like a Hardcore Henry re-mix, with a Korean flavour.
This is run and gun, beat em, cut em up, style of film, with a video game vibe. It worked with Hardcore Henry but somehow this one just doesn't quite pull it off.
I think part of the reason for that is unlike Hardcore Henry, its not quite as well paced or polished. Its back story is a bit thin too, not really adding much to the proposition. The result feels somewhat aimless and a little bland.
In short, moderately watchable but fizzles when it needs to burn.