Game Of Thrones Season 8: 11 Characters Who Could Kill Cersei Lannister
8. Tyrion Lannister
The valonqar prophecy made by Maggy the Frog - "the valonqar shall wrap his hands about your pale white throat and choke the life from you" - never made it into the show. If it had, then perhaps more would be made of the idea of Tyrion killing Cersei.
In the books, she firmly believes that he is the valonqar (which is High Valyrian for 'little brother', although it isn't necessarily gendered), which feeds into her hatred of him. It's a different matter on the show, where we can't count on the valonqar prophecy (although it's unlikely to be Tyrion in the books either), but it could help inform things, since a number of the best candidates to kill Cersei do fit anyway.
Tyrion himself has mentioned his hatred of Cersei plenty of times, and even just a couple of episodes ago was joking about marching down to King's Landing and killing her. He's tried to show faith in her a couple of times lately, and has been left wanting both times. If his trust has truly run out, and he gets the opportunity, then he might be prepared to do it. He's killed one family member already, after all.