My friend Sandra sent me this e-mail and I promised I’d post it to see if anyone has some clever ideas : )
Hi Nic
I am rewriting a few stuff for my other book called Love Fades?
What is worse than betrayal?
My take is apathy or revenge (the concept is when you seek revenge, dig two graves)
Can you ask others as well so I can have some ideas to work with?

Abandonment? (It's kind of like apathy, though.)
Violence/Domestic Abuse/Rape
Hmm…that's all I've got at the moment.
tee, hee, hee…… Okay here it goes….
20 fresh jalapeños
kneeling on rice
hog tied, blindfolded, left overnight
hot wax
good ol caning
binder clips to the skin
and my personal favorite
the violet wand
http://en.wikipedia.org/wiki/Violet_wand
Well you have your garden variety betrayal, but when it's with a friend/relative it's sooo much worse.
I'm thinking maybe mind games could be worse…if they deliberately manipulate you into doing/believing something to serve their own purposes.
Complete indifference (maybe the same as apathy?) could be horrible if the other party is still smitten.
Abuse…self abuse…the death of a child or spouse…That's all I can think of. 🙁
Apathy fits the title better, but it really depends on the characters. I'm more of panster writer myself, but probably the best way to go is to write out the characters and figure out their relationship first. Then decide which of those three – betrayal, apathy, revence – would have the most impact.
Worse than betrayal? Maybe when the MC has brought it upon himself or herself: caused it to happen.