In order to remove bad links you have to do 2 things
Make a link removal request to webmaster
Use disavow tool to notify google about those links which you can’t able to remove.
If your site is already ranking and good standing, it is essential to conduct link removal activity. Hence I recommend you to do so.
1st step is to Make a link removal request to webmaster
For this step first you have to find the entire bad link and the webmasters associated to each link and politely send a link removal request email.
Points to remember while doing this are,
The removal process can be challenging and tricky, You can’t remove all back-links
Personalize each email sending to webmasters
Always send a follow up to make sure your message was received
DON’T threaten the webmaster
Never pay for link removals- if webmaster ask money to remove don’t pay them, remember you can disavow links which can’t removable.
2nd step is Use disavow tool to notify google about those links which you can’t able to remove.
You can disavow from here: www. google.com/webmasters/tools/disavow-links-main?pli=1
To do this Get all your unmemorable bad links in a text file and upload this file to disavow tool.
Its take weeks according to Google to process disavowed links.