It depends on the child. Some children are lovely (gentle, calm, reasonable, happy, quick to laugh, interested in stuff, etc). Others are a mix. They have their good days and their bad. Some children, however, are a nightmare. There’s no getting round it. And it’s largely down to genetics. Think how often you read posts on here that go something like this: “my teenage daughter is horrible. She’s rude, selfish, lazy and entitled. No one in my family can stand her. God, she’s turning into her father. That’s exactly what he was like - no empathy, totally narcissistic. I have two other kids, a boy and a girl, and they’re nothing like that. They have their bad days, but they’re basically good kids - kind, polite, hard-working. I just don’t know where we went wrong.”
Truth is, you never know what you’re going to get. Just think how amazingly different the kids are in a big family. You can make a difference of course (lots of love and hugs, teaching them good morals, and so on), but genetics have the final say.