you mean what is the the difference between them I have never heard of soft corner before, while to have spot for is to like someone to have a crush on someone is to love him or her with all your heart

Soft corner makes no sense. I've never heard it before, except maybe when playing pool. But it is not related to having a soft spot or crush. To have a crush is when you really really like someone, like a girl or boy, but you are not dating them. You would like to, though. You can also use it to refer to someone like a celebrity that you like but will never probably even meet. I have a crush on Yuri (from SNSD). To have a soft spot is different. It is not about liking someone, but about being good to someone or helping them. You can have a soft spot for kids or for dogs. It means no matter how tough you are, you would still be good to someone or something, or help them out. The boxer had a soft spot for puppies.