This trope can range anywhere from horrible to great.

Donald Gennaro from Jurassic Park - He wasn’t a coward in the original novel, he fought dinosaurs with his bare hands and was pretty heroic. The coward in the book who abandons the kids is Ed Regis, who was completely cut from the movie and combined with Gennaro. I really hate this one he was one of my favorite characters in the novel only to be merged with Regis and made the coward of the movie. They really missed out on huge potential by not keeping Regis and Gennaro separate, he has some of the best scenes in the novel.

John Hammond also from Jurassic Park - Similar to Gennaro, he’s way different in the original book. He’s actually a villain. In the movie, he’s made to be this loving grandpa who wanted to amaze the world, but in the novel he’s basically a dark Walt Disney. He makes the park purely out of hubris, ambition, and greed, and doesn’t care for his grandkids anywhere near as much as in the movie and knows he is putting everyone he invited to the park in huge danger. He thinks he can control nature and pays the price for it. This one isn’t really good or bad, both versions of him are excellent, but I would definitely like to see the villainous Hammond on screen at some point in a darker adaptation that follows the book exactly.

The character was drastically changed from their original version