It’s a very good question, which changes I feel almost on a daily basis.
At times I would have echoed a lot of players, in saying patience.
Other times, I would have said something similar, in my ability to fold strong hands (slightly better at this live).
Recently, I would say my ability to understand ranges and putting people on hands.
There really is no one thing, in that we have to be able to use everything we’ve learned in the past and apply it to each situation.
My birth in poker came 15+ years ago, and right off the bat, I was playing home games with very high level players who turned out to be quite successful at poker. In fact, one of them has won 1st place in major events multiple times (carribean), as well as been the most successful winner online in a given year.
I went a different route in life, and devoted my attention to other aspects, and likely will have to again when work picks up after my most recent lockdown.
With all that being said, I will sum up to say that as a result of all this combined, my best quality as a poker player may be my experience.