What will most affect the direction of a putt?

The direction of a putt is predominantly influenced by the face angle at impact. The face angle determines where the ball will start its initial line after being struck. If the putter face is aimed directly at the target at the moment of impact, the ball will roll towards that target line. Conversely, if the face is open or closed relative to the intended line, the ball will deviate from that path, regardless of other factors like speed or mechanics.

While other elements like distance of the stroke, grip pressure, and ball position can affect the overall mechanics and execution of a putt, they do not have as direct an impact on the intended direction at the moment of impact as face angle does. The alignment of the putter face needs to be precise for a successful putt, making it the primary factor in determining the direction in which the ball will travel post-impact.