Unfortunately I have alot of people like that on my mom's side. I do my best by staying away from them and keeping my distance. Salaam/w'salam is the furthest I will go with people who wish bad for me.
However, I was told recently that Islamically it is a huge sin if you don't keep relations with your family members. So I guess to each their own.
Exactly what I do. But I always do well wishing to them. Keep asking about their khairiat and keep giving them courage when they need and when they have some problem I give them dua and mashwaras. And keep asking them.
Main budtameezon aur budkhuwahon ko bhi pyaar ki maar marta hoon.