The cards with the ugliest artwork are the Silly Girl and the mouth-breathing pigface N card Megumi Komoto.

Also, an honorable ugly mention for Risa Shimozono...I couldn't stand that Gambit event where she was one of the key/case distributors. What's worse, I keep getting her in random chance spins. It wasn't so bad when she had the card reveal tear running right down the center of her face and I could imagine it as a huge, puckering scar, but alas, she's progressed beyond that now.

On the other hand, cards that are particular favorites of mine are Yuri and Aoi Kashima for their alternate careers outside of PPS.