Change your preferences here.
Deals damage and has a critical hit rate one stage higher than normal. Assuming there are no other critical hit modifiers in play, this move has a 1/8 chance to get a critical hit instead of a 1/16 chance.
Shadow Claw is normally an inferior option on quite a few physical attackers due to its limited coverage, but is a useful coverage move on a select few physical sweepers like Excadrill and Blaziken. On these few Pokemon, Shadow Claw is able to easily dish out a lot of damage to bulky Psychic- and Ghost-types like Giratina who would otherwise laugh at any of their attacks. Outside of Ubers, don't expect to see it much as physical attacking Ghost-types are rare, and most other Pokemon would rather make use of the more powerful Crunch or Pursuit when available to them (both of which achieve much of the same coverage as Shadow Claw). In fact, the only Pokemon that will really ever use Shadow Claw as their main STAB attack is Banette, who doesn't even see much use in NU.
Night Slash has the same Base Power, same critical hit ratio, and hits the same types for super effective damage, but is not very effective against Fighting-types in exchange for hitting Normal-types for neutral damage.