Game Of Thrones “villains” (using the term loosely since most of the characters of ASOIAF are various shades of grey) tend to die karmatic deaths.
Theon Greyjoy betrayed The Starks and then was betrayed by his own men after taking Winterfell. (I guess this one is more of a metaphorical death than an actual one)
Joffery slowly tortured and humiliated his subjects. He died in slow agony from a fatal poison at his wedding feast.
Janos Slynt murdered Eddard “Ned” Stark and then was murdered by Eddard’s son Jon Snow.
Tywin Lannister one of the most powerful men in Westeros and claimed to do everything to further his family was murdered on the toilet by his son.
The Mountain died (or at least suffered greatly in the TV show) from Oberyn Martell from the rape and murder of Oberyn’s sister. Which The Mountain had continued doing since “The War Of The Five Kings”
Stannis lost “The Battle Of Blackwater” from The Tyrells joining The Lannisters against him.
The current villains of the series are Roose Bolton, Walder Frey, Ramsay Bolton, Cersei Lannister, Littlefinger and Varys.
Cersei Lannister is likely to die at the hands of Jaime. The only people she arguably cares about more than herself (her children) taken before her and the person she always thought she could control (Jaime) being her undoing.
Littlefinger will probably die from Sansa. His lust for her will have Littlefinger blinded to Sansa learning from him. Just like a tragedy for all of his cunning and manipulation Sansa is Littlefinger’s fatal flaw. Once Sansa finds out about Littlefinger’s role in Eddard’s death then his fate his sealed.
Roose Bolton and Ramsay Bolton will also die. Roose and Ramsay gained power through betrayal. So one of them will murder the other. Ramsay will probably kill Roose (to subvert Roose being a cold cautious player of the game) and Ramsay will die by Reek/Theon Greyjoy.
Walder Frey murdered Robb through underhand tactics and betrayal. He will die from The Brotherhood Without Banners (probably led by The Blackfish) using the same underhand tactics against him.
That only leaves Varys. I doubt that he will live til the end but I don’t know who will murder him. Perhaps Arya through warging because Varys despises magic?
The lion doesn’t concern himself with the opinions of sheep