I'm happy that my grandfather is currently dying a painful and suffering death and I'm kind of happy about it because he finally got what he deserved.
What did he do to deserve such a horrible death?
He was quite a staunch atheist who was always poking his nose in my affairs, I can't stand him.
You shouldn't wish a painful death on someone for such petty reasons. People are nosy all the time and there are millions of atheists. It doesn't mean they deserve to die.
I just don't like anything about him. Fuck him.
It's understandable to not like someone, but you should at least have the grace to wish them a peaceful death. By letting go of your resentment towards your grandfather, you'll become a better and mature person yourself.