Nyanmato What I'm recommending is a fairly well known novel, so you might have already read it. Still, if you haven't then you're in luck because it's fully translated and completely free to read and should that change it's also on WuxiaWorld (it was translated over there, not sure why it's also here but I won't complain.)
Can't say for sure if it'll be what you want, because "evil" can be many things. If what you want is catharsis through an "evil" MC that brutally murders, rapes and pillages his way through the story, then this novel isn't what you're looking for. The MC in this novel is more along the lines of a psychopath; cold, cunning and ruthless.
https://www.webnovel.com/book/8058923005003605
https://www.wuxiaworld.com/novel/warlock-of-the-magus-world
Recommendation
BerriApplepi muahaha, no it's good, since it has female MC i assume she's a black belly?
PersonMcpeopleface ah warlock of the magus world, it has been lying rotten in the corner of my library if not for your comment, thanks i almost forgot it.
lynerparel nah, it should be good, you'll know jap novel seirei gensouki?, It has a Wuss Mc who too scared to confess his love but ended up being cuckolded, and you know what did he do? He repeat the same action and even complies to order of his enemies and rivals. I'm just sick of it, hey man thanks for listening my complain XD.
Nyanmato Not that much but her character as a villain would be shown in the main arc of the story 
BerriApplepi no no, i have read it and that doesn't matter at least she have firm will and know how to draw a line (oh god now i look like my boss) , and well it should be good to pass my time. Thanks for making such good novel (in my taste LOL).
Nyanmato Thank you! I hope you'll continue to enjoy it! I'll try my best to make it interesting as possible 
All these shameless advertisers... But do not fret! As I am here!
https://www.webnovel.com/book/7996858406002505 Reverend Insanity, a very original plot and a non-god like MC that has powers that make no sense. Also, the character building is very nice :3
https://www.webnovel.com/book/8058316805003405 The next Is I shall Seal the Heavens. A very popular book but also very enjoyable. This was one of the last books I read and I really enjoyed it. The MC is not evil and actually does perform some decent acts but he definitely is not a hero, in fact, he in on the border between evil just dont get on his bad side.
I hope this helped ;p
Nyanmato Might as well throw in my two cents...again.
https://www.webnovel.com/book/8324027206000305/Tales-of-Herding-Gods
Been my favorite novel on this website for about 6 months or so? The synopsis is shit and the reviews on NU are also shit, just give it a read when you have time, preferably sooner rather than later as it's going premium soon (was supposed to go today) so unless you wanna pay more than necessary get on it post haste.
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This is if you are alright with it being an original story.....
My MC is more delusional and cold.....
The story is just about a boy who was pushed away by society and then one day he found a bright light that gave him 2 powers.... After that he decided to become a careless cold god... and his best friend is there to stop him...
https://www.webnovel.com/book/10530189005055505/Between-Light-%26-Dark
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Link Pc
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Give me a opinion
Nyanmato
Hmm, I got two Eastern Fantasy ones that are not power fantasy and the main character is ruthless/anti-hero/evil(kind of).
Consuming Earths, Devouring Skies - This one does take a fair amount of chapters to get past his stupid/wuss/retard stage, but once he does it is amazing and he is a hilarious character. Sigh.... crippling a sect leader because the sect leader flattened his cake when they released their aura pressure where he was eating.... those were the days...
Monarch of Heaven's Wrath - This one has an MC that is incredibly ruthless and can be a bit bestial early on (due to a few reasons).