Hi! It's a manga. I used to read it on [redacted]. I didn't bookmark it because I thought it would be easy to search since the translated version used to be regularly updated but nope... I couldn't find it anywhere (not even on MangaDex), not even by using search terms like dragon, dragon MC, and so on. So... please, help!!! I really really wanna read it again for the revenge scenes are awesome. They are not mild or gutless like the usual mangas. Manga Description: The MC is a male who was reborn as a baby dragon. While in that form, he almost died and a girl saved him. The girl is a noble lady. She is apparently considered by everyone a villainess and is, therefore, continuously and mercilessly bullied for a long time even by the maids. She has a sister (or is it cousin?) who is supposed to be a heroine... I think... and she has the power to kinda brainwash others... the power works brilliantly on weak-minded people by manipulating their bad thoughts (like envy). Feeling indebted, MC swore to protect the villainess. I don't know who gave the power to the heroine but at some point, MC manages to hurt her so, while hiding she tried to ask for help (or more power) from that entity but the entity was kinda disappointed in her, for some reason, thus it turned her into some kind of angel-like (in term of appearance) monster. I think she became mindless too. I don't know what happened after that. Some notable scenes: For revenge, MC destroyed the ass of one of the heroine's supporters which caused the guy to be wearing diapers for the rest of his life. I think the guy was hung naked on the gate... or was it another guy? Not sure... There is a gay priest with bulky built helping MC and the villainess but he couldn't do it openly for some reason...
I believe it's this: Saikyou no Mamono ni Narumichi wo Tadoru Ore, Isekaijuu de Zamaa wo Shikkou suru. It's not a dragon, so no wonder you didn't find it