Despite the instructions, I'm gonna underfeed my stepbrother's goldfish.
Don't you think that'll kill the fish?
I know it will and if it doesn't, I'm going to throw the fish in the river as soon as he leaves for college.
You can't just kill your brothers pet. That's a terrible thing to do to him and the fish.
I'm slowly killing him, and couldn't care any less.
If your stepbrother asked you to care for his fish and finds out you intentionally killed it, that'll not only upset him, but break his trust.