Mankey's sprite from Red/Blue isn't much to cheer for either:
The entire concept of "joints" is simply forgotten in this sprite. Its legs have no knees, and the arms appear to curve at a constant rate without the need for elbows. Its tail also feels awkwardly long, considering that it's supposed to be attached to the middle of its back. Also, the pose.
And who can forget Golbat?
What was up with those eyes? If you don't notice, they are wider than its body, and also placed at slightly different levels. And the
sideways tongue? Or the body randomly leaning to its right? Or even the feet? This is one messed-up sprite.
Then there's another Victory Road frequenter, Machoke.
Here we have all sorts of issues. The eyes are mismatched, and gives Machoke a face like a stoned frog. Its right leg is obviously bigger than its left. Considering how much better Machoke was drawn in Yellow, with the exact same software and hardware limitation, this sprite is a seriously poor piece of work.
Vileplume is also... interesting:
Official art has always portrayed it as purple or blue, with a kettle-shaped body covered by a large flower. However, this image seems to suggest a long stem between the top of its face and the underside of the flower, otherwise you wouldn't be able to see both the face and the flower in that perspective. Also, it's inexplicably black. Well, that being said, no later sprites did Vileplume justice either. If you look at its Yellow sprite, it's shown that the flower starts pretty much right above the eyes, as if it was wearing a large hat. All later games, however, show the flower from a top-side angle, but also its entire face. The FRLG sprite seems to be the closest one to the concept from the official art, the rest take huge liberties regarding the top of face - bottom of flower distance.
Last, and finally not one from R/B: Raikou from Gold/Silver.
For the record,
this is the official artwork of Raikou. Notice anything missing? Yep, that's right, half of its face. The fangs are missing, the white face cover (which must be really impractical when Raikou is eating, but oh well. At least it can open its mouth, unlike Kyurem) is missing, and the white fur encircles the face, instead of disappearing underneath its black "cap". Also, the fur on its back is orange instead of purple, and its claws are too (they should be white). I know G/S sprites could only contain two colours besides black and white, but there doesn't even need to be any orange on Raikou for it to look right. At least not compared to the required amount of purple.
Either, this sprite portrayed a beta design for Raikou, indicating a communications screwup somewhere along the line, or somebody did not show up sober to work one morning. Despite Gold/Silver being launched in Europe almost
a year and a half after they were in Japan, and Korea got them another year later, the mistake was not fixed in international versions of the games. I think that makes Raikou's G/S sprite the worst ever in Pokémon history.