Well, human beings are surprisingly fragile, so not a huge amount of violence is actually needed to incapacitate or kill (one blow of the hand can suffice). But it probably depends on the style of the story and, as
@The Crawling Chaos says, the dramatic context. The violence in a Bond film is very different to that in a thriller like
Marathon Man or a kung-fu film.
There are a lot of factors that determine if the violence is too much. Off the top of my head you've got: how "light" the tone of the story is (Bond is quite light, Bourne much less so), how skilled or superhuman the fighters are, what the fight means in terms of the drama of the story (the heroes of
Watership Down are just rabbits, but their deaths are really traumatic), how much the villain has "earned" their fate, who is meant to be reading the story and consistency with the rest of what's happening.
Some older writers were very good at this. Because they couldn't include much violence, so they used suggestive phrases. In
King Solomon's Mines, an elephant is described as tearing a hunter in two, and the rest of the gore is up to your imagination. Likewise, the hero in
Rogue Male throws an assassin onto an electrified rail line, and all we hear are screams and a sizzling sound. Nice.