I want to watch/read more content that features evil protagonist. Please do not recommend shows/manga that have protags who are "fake evil".

Manipulative and scheming MC's are welcome (they don't have to be evil, but they must not "good" or morally in the right). I do not want to read a story where the protagonist is "bad" but there's a bigger bad person or thing that they must defeat. I'm absolutely tired of reading/watching stories like that.

Already watched One Outs, Code Geass (not evil but added because I do not want anyone to recommend this to me), Youjo Senki, and Akagi a long time ago too.

Gu Daoist Master (Novel)

It's the best stuff I've ever found with an evil protagonist, it has it's associated manhua (but after some chapters the drawing quality drops). I'd recommend you read the first chapters of the manhua and if you liked it continue with the novel .

The protagonist isn't randomly bad or like some manga MCs that are "evil" but is just an excuse to show SM.

He just seeks everything and anything to survive .This end goal is to achieve "true freedom" by destroying the laws of that world (it's not a random never ending power scale ) .As you asked he is very manipulative and scheming ,the best part is that his enemies also use their head and there are some crazy plot twists and many of them end terribly for the MC.

He's a bit too ruthless at times (if you get past the man beast gu there isn't anything worse after that,except maybe the end of the bone mountain ark). If you can accept that then I can asure you he doesn't do anything as crazy/sick. (If you end up reading it ,check it out in a website with comments ,they're gold)

Haha I'm actually an avid reader of Reverend Insanity. It truly is a top-tier webnovel.

Another one that I've read is Warlock of the Magus World, this one is good too.

Death Note.

You can read lesson of the evil it's the story of a literal psychopath working as a teacher......

You can read lesson of the evil it's the story of a literal psychopath working as a teacher...... also trail of blood.......for that one you can watch super eyepatch Wolf's vid on it

Anne Freaks

"We can not resort to simplistic or extreme solutions which substitute myths for common sense." ― Jimmy Carter

They're great , I can't think of anything of the same quality.

His motives are pretty neutral (I read it ages ago)
Darker than Black