A lot of the top-notch, well-known subscription-based SEO tools out there have a keyword difficulty ranking system.
They are, however, not consistent.
One tool might say that a keyword is very easy, while another tool would say that it's almost impossible.
With that said, you should also focus on the domain authority of the top 5 sites that rank for that keyword.
If you have a tool that says a keyword is very easy, take a look at the site.
Know them on those SEO tools you are using.
What is their overall domain authority?
How many are the organic keywords that they rank for?
This should give you a holistic picture of how easy it truly is to rank that keyword.
That's why I try not to get excited when I find an "easy" keyword when I reverse-engineer big competitor domains.
What excites me is when these tools say NA or not available.
This tells me that there is really no incentive for these competitors to try to rank those keywords.
If those keywords are auto-suggested by Google when I try to enter part of their words into Google's search box, I pay attention to them.
What really excites me is if they are thematically related to other keywords that I have solid information on.
You just have to connect the dots.
A lot of this is detective work, but there is a lot of value in picking and ranking keywords that are "off the radar" as far as the big SEO tools go.