Like someone posted earlier, not one bull is 100 percent but you have better chances with certain bulls than others, the 2 Unforgiven calves Ive been around were almost to gentle, the best calf we have had was a Full Flush, go figure, the worst was a Friction (Full flush son), great calf just a ticking time bomb on the halter.
Some of the disposition can come from how they are handled when their started, how they were de-horned, or some past experience they may have had with people. Full Flush's were know for letting past experiences determin their future behavior. You have to look at each calf on it's own merit, with their genetics as part of the process.
I loved the looks of the Frictions but would find it hard to buy an other one. I am guilty of basing it off of one calf.