I want my mum's partner to hurry up and die of cancer
Why do you want them to die?
I would feel more at ease if he was dead.
Wishing death upon someone your mom is close to is wrong. She cares for him and would be upset if he were to die.
I didn't wish for them to die, I just said that I want them to.
That is essentially the same thing. Try to get to know him more, maybe your opinion of him will change and you can like him.