Here are the best checkers in my opinion:
1. SEO Moz: https://moz.com/tools/rank-tracker
2. Majestic SEO: https://majestic.com/
3. SEO Glass: https://www.link-assistant.com/seo-spyglass/ (it is a program, not a site)
4. Raven Tools: https://raventools.com/
5. Ahrefs: https://ahrefs.com/
All are good and do a pretty decent job!
Exactly on that topic there is an article which you can read here - https://www.matthewwoodward.co.uk/seo/tools/best-backlink-checker/ a comparison between all these tools. Personally I like SEO Moz....
You can also use Scrapebox's premium plugin called - Rank Tracker. It also tracks all your positions in the Search Engines. Here are 2 videos explaining...https://www.youtube.com/watch?v=15fzUFKZ7a8https://www.youtube.com/watch?v=y6fDhSAa8qI