Tahm Kench and Evelynn may have a shot.
Tahm regularly preys on desperate people to grant their wishes, but his intentions are pragmatic as he manipulates his victims into becoming addicted until they suffer the consequences and are left at rock bottom, feeding on their addiction and the despair they feel when they lose everything and even eating them whole. In one of his myths he slowly dismembered one of his victims until she had very little of her body left. And he has full moral agency since after he ate the gambler, he told his wife that he couldn't control his demonic instincts but it was a lie to lower her guard before eating her as well, and he even boasts about it in his trailer.
As for Evelynn, she enjoyed the suffering caused by the Rune Wars so much that she took on an attractive form so she can allure humans to torture them in agonizing and drawn-out ways such as flaying to feed on as much suffering as she can before they die. She formed a cult that does her bidding, killed Shauna Vayne's parents turning her into a ruthless monster slayer, and her end goal is to plunge Runeterra into chaos so she has a worldwide supply of agony to feed on. Then in Legends of Runeterra, she recruits several demons like herself to find more victims, torturing them until they're left as soulless husks. And Evelynn also has clear agency seeing as she can understand humans' emotions and desires and can act benevolent as part of her facade, as with most of her fellow demons (for example Solitude pretends to be pitiful to make her victims sympathize with her, but in truth she's sadistic and makes fun of them for being fooled by her). Speaking of, Vora is unable to control her hunger showing that all the other demons are only restraining themselves, and Evelynn is one of them.
There are hints that they both respect each other, since Evelynn tells Tahm that she likes him but he should stay out of her way, and pointing out that he "hasn't missed a meal". But even then these are only in-game voicelines and are the only times they've interacted, they don't have any interactions in LoR so it's fair game.
