Is it true that Darry is never sorry for anything he does like Ponyboy says?

No, it is not true. There are multiple scenes throughout the novel that depict Darry feeling sorry for the way he acts toward Ponyboy. In Chapter 3, Ponyboy returns home late after falling asleep next to Johnny while they are looking at the stars. Darry is sitting up reading the paper when Pony returns. Darry gets angry with Ponyboy and slaps him in the face. Ponyboy runs out of the house and Darry yells, "Pony, I didn't mean to!" (Hinton 50) Later on, in the novel when Ponyboy is sitting in the hospital, Darry walks in and begins to weep. Ponyboy finally realizes that his brother cares for him. Darry was under a lot of stress trying to raise Ponyboy and provide for the family at the same time, which is why he lost control and hit Pony. In Chapter 12, Sodapop becomes fed up with the way Darry and Ponyboy fight with each other. Sodapop runs out of the house, and Darry and Pony are forced to chase him. When they finally catch Soda, he laments at the way his brothers have been treating each other. Darry realizes that he's been too rough on Ponyboy and agrees that they will not get into any more fights.