Purrloin. Dear god, Purrloin. This thing sucks so much it's unbelievable. Purrloin is fast but it is weak as hell. If Purrloin had bite (which is befuddling as to why it doesn't) in its early movepool he would be okay. Since it doesn't he is banished to the realm of failure.
His best attacking options are what? Scratch, Cut and Fury Swipes until level 15 where it learns Pursuit. Pursuit would have been fine if it learned it earlier. It evolves at level 20 becoming a little stronger and good enough until you can catch something better. He has some good moves such as nasty plot, but where are the special dark moves? The best moves he has are night slash and sucker punch.
Purrloin is pure fucking garbage.