My money is on John Wick, but that could just be because Agent 47 as I know him is a blundering fool who’s over the top plans end up devolving into using a pan to try to kill a security guard firing a gun at him.
Agent 47 would win before Wick even knew it was on. Doesn't matter how good you are if you get taken out from over a mile away with the first and only bullet fired in the engagement.
Better yet, 47 would simply disguise himself as the vet and put a contact poison on Wick's dog the next time he was brought in.
I never really thought of Wick as an assassin. He feels more like a gunfighter. He favors a relatively small kit and likes to get up close with it. 47 on the other hand is all assassin. He'll mail a banana peel to your neighbor and the next thing you know you've snapped your own neck getting out of the jacuzzi.