Personal advice from person who suffer from Negative SEO for very long time,
Don't ever ever relied on Negative SEO to achieve anything,
you only will get your personal revenge and your competitor will know what you did and they will try to hunt you too,
That's will be endless(childish act) circle the only winner are google and you all gonna lose .
I'm not telling you to be saint or good person in life, but because it's simply doesn't work, you will only get Google spam team get more attention to your niche at the end screw it to all of you .
If you want sht on the floor so nobody will stay/live there go ahead and take you time, if you don't, move along in your life and focus in something else .