First of all, someone who got kids for the right reason. Not as an accessory or an Instagram model. Not as a way of curing loneliness, lack of meaning or self worth. Not as a projection surface for their own narcissism, to follow societal norms or "just because". Rather for believing in raising a child, believing that you could foster them into good, secure people.
Then, I am not really sure. I've spent a lot of time thinking about this because there is this idea that you should internalize your own ideal parent if you didn't have healthy, real life counterparts. It's a work in progress. But I'd like to think that first and foremost they should be aware that the child is their own human. They have their own personalities, talents, fears, dreams and insecurities and those shouldn't be minimzed in favour of what the parent wants to see. Which is often themselves. Then I think a certain amount of childishness is crucial. They need to be able to empathize with the child, to see the world from the child's own perspective, and able and willing to actively play. I do think that most adults would benefit from that. Then ofc sensible, nurturing, patient, flexible, genuine (to a degree, please do not be too honest with your children) and with firm but loving boundaries.