Stain
Stain’s original design had more weapons and tools than his design in the anime and had a mouthpiece that was not kept in the manga or the anime.
Himiko Toga
Himiko Toga’s character design of being a yandere, someone who is dangerously obsessive towards others, was decided with her original design. She did appear to be more unhinged in her original designs, with blood dripping down her mouth, showing her leaning into her vampiric tendency. Otherwise, her character design matches up extremely well with the original sketches.
Shigaraki
Shigaraki’s design in the original looked way creepier than the one that they decided on. His eyes and mouth were black and hollowed out, but he had significantly fewer hands on his body. He also was supposed to have a wired cape with fewer accessories, making his design way simpler.