I have this website which is relatively new and I am trying to rank it in Google. But, I have this enemy who keeps building bad/spam links to my site. So, every time I see some rank improvement in my site, he builds spam links to my site and my ranking slides down in SERP's. I am disavowing those links as soon as I see them but, for how much time I am gonna do that! Is there any tool or trick using which I can disavow such links automatically?
No there is no way to disavow the links automatically. In that case there is a chance to disavow quality link.
There isn't a way to disavow links automatically, you can only manually disavow them or do so using the Google Disavow Tool.