Speaking of attributes in general, there is no clear winner about which one is the best. Every attribute is as important as the one before or after it, because each attribute makes a player whole. If there were an attribute to pick out of every single one in the pool, it would definitely be Passing. Why passing you may ask? Well, naturally the ability of a player to pass very creatively and confidently is highly undersought after. Now, to break it down why I would recommend it

If a player has low passing, his ability to create plays is highly decreased. If you cant land a pass to another player, you will lose momentum and therefore will lose grip on another team and the most important thing that it messes up is the potential scoring situation. The higher the player's passing ability is, the higher his worth is offensively. A players high passing skill allows him to make more creative passes which most of the time results in catching the enemy team off-guard, allowing other forwards and why not also defenders explore different options in their own offensive area. This is why I would recommend EVERY player to invest their skill points in passing, because it is singlehandedly the most important attribute for every role, from defensive defenders to playmaking forwards.