SpyFu is the best tool to find Competitors backlinks and the keyword in which they are ranking.

SpyFu allowed me to check them for a "free" trial. Actually, this meant that I was able to pay for the tool and once I'd explored the features, I was able to cancel my subscription instantly by using their chat feature to cancel and ask for a refund. They gave me no hassle and I was instantly canceled and refunded. Never seen this before, no fuss, no questions, just kindness. I love their tool for spying on competitors Google Ads, but the competitor I was searching wasn't running ads, so I needed to allocate my clients spend elsewhere. That said, I trust SpyFu because they're here to help, and it's refreshingly easy to use with no strings attached.

This is the most complete tool for SEO. It is easy to use to find competitor keywords. Its best feature is finding the PPC keywords for the competitors. It is easy to implement into my existing workflow. It can become quite an integral part of me.