Do you move forwards or backwards on the King's Cross Chance card?
Movement in Monopoly is always forwards (in the direction of the arrow on the Go space) unless otherwise specified (such as the "Go back three spaces card").  The only exception in regular monopoly is going to jail, which is usually written as "go directly to jail" to signify the difference.

Some older editions of monopoly had a much clearer version of this card (noting that Reading Railroad is the equivalent of King's Cross):


  Take a ride on the Reading. Advance token and if you pass Go, collect $200.


It is impossible to get to King's Cross/Reading Railroad from a Chance space without passing Go.  It says "if you pass Go" because that's the way all the other Chance cards are worded.  This card would be clearer if it said "when you pass go, collect $200" or "collect $200 for passing go".