Why is the guy so vengeful, cold and revenge mentality for rejecting him, despite years have passed?

[happyfoetus]

[20yearsolder]

You must have really heard his little fucking ego. If you treat you that way why do you even associate with him. Tell him to go fuck himself and stay away from you

[SnowedIn]

One possibility is that that's who he is. Alternatively, you hurt him some way and this is his immature method of coping.

[Summeroflove]

Some people can't take rejection. They feel they are entitled to another person. Just like move on...