Karma will get you back for having negative thoughts....

You might have to wait a while.

then you've got some karmic slap-down coming by the sounds of your post.

Of course, if magic, karma, and Santa Claus do exist, I guess I'll be more shocked than anyone.

What a horrible thing to say.
Careful, karma could well decide to give you the good ol' "right back at ya!"

like you deserve so much good karma haha ... not

so i guess that means 'brunch' is off?

this sounds a lot like someone I know. Maybe Karma is currently biting you in the ass? But you likely wouldn't ever have enough self awareness to see what you've done as the cause of the current situation.

What is it I've done?

Karma is action based. It's the actions not the thoughts of a person that karma reacts too. I've seen it in action many times.

Let's back up. There's a person who is horrible. You wish they were dead. That's horrible.

We could assume that you are both horrible but instead let's ask what we could do to help that first horrible person.

Karma is not a cosmic scorekeeper, keeping stats on the naughty and nice. Karma is understanding the consequences of actions.

Be compassionate. It's better for everyone.