A superhero movie is only as good as its supervillain, and some of these villains would have made very different movies.
Does DC Comics have any unused comic book characters? - Quora
Design villain concept art for film., Illustration or graphics contest
Street Fighter 6: Character Concept Art / Unused Designs (Wtf happened to Blanka) : r/StreetFighter
Concept art of the cinematic villains compared to their final design : r/batman
Design villain concept art for film., Illustration or graphics contest
29 Unused Marvel Concept Art Designs That Would've Changed Everything
Christy Box
29 Unused Marvel Concept Art Designs That Would've Changed Everything
20 Unused Supervillain Concept Art Designs That Would Have Completely Changed The Movies
Suicide Squad: Joker concept art proves Jared Leto's character almost looked much, much worse, The Independent
Some more recent unused concept art designs I'd like to see reused in future projects : r/StarWarsCantina
29 Unused Marvel Concept Art Designs That Would've Changed Everything