Had a couple bad experiences.
The first- old school limousine bull. The words flight or fight really suited his progeny. Thankfully had just a couple, but that was more than enough. Have only one his daughter as a cow. The only good tempered from all his calves. 12 years old at the moment.
The second, and very recent- used "easy calving-heifer safe- bull on some females, which shouldn't have been crossed with him. Some calves were okay, easily calved, but some were some scale wreckers. The biggest calf from 26 months old heifer- 121lbs bull calf. Needed assistance with a jack. The biggest from a second calf cow- 139lbs. This one was alive for a couple hours, but never stood up. Still using that bull on a very few cows, but never on heifers. His smallest calf was 83lbs from a small heifer, but she actually always has small calves.
And the third, the most recent one- charolais bull. The AI man didn't had the bull, which we really liked anymore, so used a new one on three cows. Two heifers and one bull were born this year. Bull died a couple days after birth, so no idea how he would have turned out, but two heifers, especially one, very very dissapointing. Both from proven cows, not youngsters, both cows are good producers, always had good growthy and nicely shaped calves. Not this time, unfortunately. Both heifers were lacking growth a lot. Have another heifer from another charolais bull and she is way bigger than those two. Sold one heifer as a weanling- 9months old 595lbs. Have left the second one, at least for now. She has mom's looks and is abit bigger than that one. She might turn out quite alright, if she'll take after her mom.