Which ghost in Pac-Man targets four tiles ahead of Pac-Man? The answer is Pinky.
Pinky is the pink ghost, known in the original Japanese game as the ambusher. During Chase mode, Pinky does not simply aim for Pac-Man's current tile. Instead, the game calculates a target four tiles in front of Pac-Man, based on the direction he is facing. This lets Pinky cut off routes and approach from ahead rather than merely follow behind.
The targeting rule contains one of Pac-Man's most famous programming quirks. When Pac-Man faces upward, an arithmetic overflow in the original game's code shifts Pinky's target four tiles to the left as well as four tiles forward. As a result, Pinky can appear to predict a diagonal position rather than a point directly ahead.
The other ghosts use different strategies. Blinky targets Pac-Man's current tile, Inky calculates a position using both Pac-Man and Blinky, and Clyde alternates between chasing and retreating toward his corner when he gets close. Pinky's four-tile ambush behavior is therefore the canonical answer, even though the upward-facing bug makes the rule look inconsistent.