Why did Zeref become evil?

Why did Zeref become evil? If he could suppress any sort of feeling of love, no one would have to die to his curse. At the same time, this caused Zeref to become conflicted between good and evil. The lack of love in his immortal life consequently turned his heart very dark.

If he could suppress any sort of feeling of love, no one would have to die to his curse. At the same time, this caused Zeref to become conflicted between good and evil. The lack of love in his immortal life consequently turned his heart very dark.