That would be hard to define because it's as individual as the rifle and the person and depends on what it is being used for. I look at the categories of hunting and target shooting. In hunting you occasionally have short range (ugly word here) shots and the bullet needs to be presented so that it stays together long enough to penetrate enough to do tissue damage.
For instance let's take my favorite bullet of all time; the Nosler Ballistic Tip. I'm pushing the 150gn BT out of my 7Mag at 3250fps. If I were to shoot a deer on the shoulder at 50yds the results may be bullet failure. Penetration may suffer and the deer could get away with a very nasty wound, only to suffer and die a miserable death. If I were to put that same bullet between the ear and the eye of that deer (same distance) bullet "failure" would certainly occur but so would skull failure resulting in a very dead deer on the spot. So in the latter case the bullet didn't fail but did exactly what I wanted it to do.
For me, Ballistic Tips are in the top four (Bergers, SMKand TSX) for accuracy and give me the confidence I need to execute a precise shot whether short or long range. They are what they are. JohnnyK.